Study Service Priority

Study Service Priority

53RD ANNUAL CONFERENCE, Gran Canaria, Spain, 5-9 May 2014

WP No. 89

Study Service Priority

Presented by PLC and TOC


Future demand of increasing capacity will need the introduction of new prioritisation aspects. An example of Service Priority is the “Best-equipped, Best-Served” concept which is emerging as a new tool for the benefits of airspace users. A description on this concept together with the relative operational and professional implications will be given in this working paper.


1.1  Global aviation demand continues to grow with emerging markets and economic expansion. Air navigation service providers (ANSP) worldwide are striving for increasing capacity and efficiency to cope with the air traffic growth and meet environmental objectives. Economic and political pressures on airspace users to reduce both costs and carbon emissions (CO2) have led to a focus on system efficiency as a means to reach these goals. Thus, air traffic management (ATM) system enhancement and modernization which include upgrades of both ground-based infrastructure as well as airborne equipment becomes essential to the future ATM system.

1.2  Future ATM encompasses a broad range of technologies and operational changes in air traffic control. It may also require organizational changes, airspace restructure, or liaison between different stakeholders within the ATM system. It is a complicated process which involves synchronization between all parties at different transition phases of the enhancement programmes.

1.3  Previously rules were set to mandate users to equip their aircraft with such technology needed to adhere to the minimum level of safety. Even if safety is still the top priority when operating the airspace, efficiency of the flights has become even more and more relevant in the operational policies.

1.4  A new concept has turned the previous ruling activities upside-down. Instead of mandated equipment, system users are requiring the ANSPs and governments to show how any new equipment can provide an economic benefit. The promise of these operational incentives are sought before the operators will invest in the on board portion of new technologies, whereas upgrades of ground-based infrastructure are usually financed by government in most part of the world. On the airborne side, aircraft operators need to bear the cost of aircraft equipment upgrade. In order to achieve the best overall efficiency in the development process of future ATM system, certain means of incentives has to be provided to aircraft operators for their investment in new systems and/or advanced technology on board the aircraft.

1.5  ATM is along a modernization path that will face the need to deal with mixed aircraft equipage. Benefits for the system as a whole can be maximised only if equipage and deployment is as fast as possible, while catering to the variety of needs. The current “first come, first served” principle may not be a suitable notion anymore.

1.6  New concepts like BEBS – Best-Equipped, Best-Served, BPBS – Best-Performed, Best-Served or MCBS – Most-Capable, Best-Served are being studied. The need to accommodate the growing demand of capacity can lead to an operational environment where users who carry most advanced equipment will get better air traffic service. One argument for this approach is to incentivise the investment in on board equipment to accelerate the rate of change. This shall not affect the safety level which has to remain at the highest level for every user.


2.1 Best Equipped Best Served Principles

2.1.1  During the Twelfth Air Navigation Conference (Montréal, Canada 19 to 30 November 2012) the Civil Air Navigation Services Organisation (CANSO), the International Air Transport Association (IATA) and Airports Council International (ACI) forwarded a working paper on the service priority item to ICAO. It stated to ICAO the need to:

a) support an industry-wide study group to consider the implications and ramifications of continuing with “first come, first served”;

b) request that this study group draft guidance material proposing alternative formulations if it thinks it’s appropriate, taking into account the issues raised… (omissis); and

c) require the study group to investigate areas for further consideration as it might identify.
(ICAO AN-Conf/12-P/98)

2.1.2  CANSO added the need to consider possible alternative approaches since the BEBS concept may cause several issues.

2.1.3  The transition from the notion of “First Come, First Served” to the notion of “Best Equipped, Best Served” (BEBS), whereby flights that are more capable are given service priority over those that are less capable, is one of the means to incentivise aircraft equipage. ICAO advocated this concept at the 6th Worldwide Air Transport Conference (Montreal, 18 to 22 March 2013) where Airports Council International (ACI), Civil Air Navigation Services Organisation (CANSO), and International Air Transport Association (IATA) submitted a working paper on the “Guiding Principles for Service Priority Policy”. It said that the notion of “First Come, First Served” can produce inefficient outcomes by slowing the take-up of new, improved and more capable and efficient ground and airborne ATM systems and procedures, and thus, needs to be complemented with the notion of “Best Equipped, Best Served”.

2.1.4  The paper states also that:

“To tactically provide service priority in a mixed capable flight environment introduces additional levels of complexity such as assessing the qualifications and avionics capabilities carried by airspace users, as well as simultaneously running dual procedure”.

2.1.5  IATA supports the migration towards “Most Capable, Best Served” principle in its discussion paper on “Best Equipped Best Served Airspace Operations” published on 1st November 2012. “Most Capable” in this sense refers to aircraft equipage, crew training, operational certification, flight planning capability and the ability to efficiently and seamlessly convey the pertinent capability to ATM. Under this concept, “Most Capable” flights would be provided with more opportunity to gain full advantage of their capability in order to maximize the overall ATM system efficiency as well as of the flight itself.

2.2 FAA

2.2.1  The Federal Aviation Administration (FAA) also proposed the concept of BEBS in its performance-based Next Generation Air Transportation (NextGen) Plan. To enable future advanced national airspace system management, it is crucial that the installation of advanced technologies on board aircraft to be concurrent with the upgrades of ground-based infrastructure (FAA proposed 5 different scenarios where BEBS could be implemented: “BEBS 1” to de-conflict airport operations and to lower weather minimums for the following airports: JFK, LGA, TEB, MDW. “BEBS 2” for SOIA – Simultaneous Offset Instrument Approaches (Paired SOIA Paired Aircraft approaches) for the following airports: PHL, SFO, EWR. “BEBS 3” for ADS-B East Coast offshore routes. “BEBS 4” for ADS-B In Trail Procedures (ITP)/South Pacific and Beyond. “BEBS 5” for NextGen Minimum Capability Priority). The idea of BEBS is an important component to incentivising aircraft equipage and rewarding more capable flights with higher priority over those less capable aircraft.

2.2.2  One possible issue that could arise is that being best equipped does not guarantee a real operational capability. The aircraft may be equipped, but the use of a specific procedure is dependent on crew training, certification and willingness to perform the manoeuvre. “Training of controllers, aircrew, and dispatchers, plus equipage are integral components of a ‘Best-equipped, Best-served’ NAS” (RTCA TF5, page 68).

2.2.3  IATA itself published on 1st November 2012 its position on BEBS Airspace Operations. It states that:

“Enabling operations under this principle is more difficult than it may appear at first; mostly due to the complexity caused by mixing aircraft capabilities within dense airspace and the consequential workload increase on air traffic control”. (IATA discussion paper and position on “Best Equipped Best Served” Airspace Operations (November 2012))

IATA prefers the concept of Most Capable Best Served with the intent of optimizing the efficiency of airspace operations. Under this principle, those operations, supported by technology, qualified personnel, and systems on the ground and in the air, that provide the best operational benefit and incentivize evolution towards agreed-upon objectives would be preferred.

Figure 1 – benefit gained by ADS-B equipped aircraft within ITP environment

2.2.4 Europe is implementing the Single European Sky (SES) initiative, though it is not identical to FAA’s NextGen Plan, but it is under the same “umbrella” of PBO – Performance-Based Operations. It aims to improve the overall performance of aviation and at the same time ensure safety and efficient utilisation of airspace and air traffic management system to all airspace users. It involves restructuring of airspace previously dominated by national boundaries to the use of ‘Functional Airspace Blocks’ (FABs), where boundaries are designed to maximise the efficiency and capacity of the airspace. The Single European Sky ATM Research (SESAR) programme is to provide future technologies and new procedures for the modernisation of Europe’s ATM system. The SESAR Joint Undertaking (JU) also consider incentives schemes like BEBS policy as part of the business case for a multi-stakeholder approach in the way forward and to counteract the “last-mover advantage” thinking of many airspace users.

2.3 Operational scenario

2.3.1 There are significant operational impacts on mixing aircraft which are not capable of executing the specific procedure/manoeuvre and having ATM being unaware of that until the very last moment. There is currently no automated means to get the “capable/not capable” information unless the ATCO is able to access the entire FPL (Richard Jehlen: “Best Equipped-Best Served” (public consultation presentation, slide 5) March 13, 2012).

2.3.2  ATCO should not be responsible for the recognition of aircraft capability to perform a requested service (e.g. 8.33, PBN, RVSM, BEBS or whatever). A request by the user to perform such flight profile (in accordance to the FPL) should be recognised as a self- certification of capability. In case ATCOs will be requested to be aware of the aircraft capabilities (e.g. “qualified” or “better equipped”), the relative information has to be easily recognised by controllers at early stage of the flight operations.

2.3.3  Except when the traffic management sets the sequence to which service has to be provided, ATCOs are usually expected to handle air traffic according to the “first come, first served” principle. In airborne operations, it is generally left to the controller’s judgement to determine what is meant by “first”. It can be first to call, first to reach an assigned altitude, first to enter the airspace, etc., but generally, controllers are given the flexibility to make this determination in a manner that maximizes the overall sector efficiency.

2.3.4  It can be argued that lesser equipped aircraft impose additional costs on the system by requiring additional work by controllers. For example, aircraft that are not equipped to fly a certain SID or STAR may require radar vectors and additional coordination between controllers. These additional services may impose greater costs on the ANSP, but charging regimes are not adjusted to reflect these additional costs. In this way, the current system could be described as “Least Equipped, Most Served”.

2.3.5  If we imagine airspace designed with capacity operated at minimum spacing then such an area could be flown only by those aircraft which have the minimum capability that complies with it. If that portion of airspace is not flown by BEBS user then it should be used for the other aircraft to permit the best use of the airspace. Surveillance systems are already used nowadays to fill the gaps between aircraft to reduce delays and get an efficient use of the airspace. Several different concepts can be considered as better equipment.

2.3.6  For example; aircraft with less CO2 emission could be permitted to fly over certain areas. Aircraft which carry advanced spacing technology could be accepted to fly along more direct routings.

2.3.7  A service priority might also be proposed based on ethical scenarios. It could take into consideration the number of passenger on board or the amount of taxes to be paid by the user when deciding who will land before the others. Some airlines have proposed ad hoc scenarios similar to this approach where they express a preferred sequence for arriving aircraft based on airline financial criteria.

2.3.8  So the notion of BEBS poses a certain level of operation complexity to the ANSP which has to deal with a mixed capability fleet, especially within the terminal area, where re-sequencing more capable flights over less capable (or capable over non-capable) flights might sometimes end up compromising the overall efficiency, safety and capacity of the system as a whole. Moreover, qualified or better equipped aircraft have to be easily recognised by controllers at early stage of the flight operations, otherwise manipulation of its landing or departure sequence, preferred cruising level or direct routing, will exert practical difficulties to controllers making the implementation of BEBS impossible.

2.3.9  Any of these considerations will have consequences in the way ATCOs provide the service. So far we treat all users the same way but this could change the way we provide the service. Mixed mode operations are to be considered.

2.3.10  IFATCA has policy on Mixed mode operations (MMO):

ATS 3.14
Mixed mode operations are defined as ATM Operations that require different procedures due to variances in airspace users’ characteristics and/or ATM design within the same area of controller responsibility.
Efforts should be undertaken to reduce existing Mixed Mode Operations by creating intrinsically safe solutions.

Introductions of new Mixed Mode Operations should be avoided by creating intrinsically safe solutions.

When safety of a Mixed Mode Operation cannot be completely managed at an intrinsic level, assessment must take place that the change in the ATM system does not increase controller workload to an unacceptable level.


2.3.11  The European Commission forwarded Working Papers on several items to the ICAO 12th Air Navigation Conference. The WP 6.1/2 is about the Best-Efficiency, Best-Served concept. Although this paper is environment-related, it is a good starting point for designing ATM systems considering new aspects.

2.3.12  In order to accommodate airspace users with different capabilities, while at the same time balance against system efficiencies and safety, tactical planning of flight operations and service provisions at early stages are required. Dissemination and identification of flight plans of more capable flights or better equipped aircraft into the air traffic flow management system before these aircraft get airborne allows easy manipulation of the departure sequence or assigned departure/arrival slot over less capable or less equipped aircraft. In that sense, more capable flights are given priority over less capable flights and are allowed to go to the head of the departure queue. In congested airports where ground delay is inevitable, prioritisation changes incorporating BEBS principles provide a very real competitive advantage for better equipped aircraft.

2.4 Financial Incentives

2.4.1  Financially incentivising capabilities enhancements are seen as needed at early stage of the implementation process. Their aim is to speed up modernization of the ATM system to a certain threshold before a critical percentage of capable airspace users as well as overall system benefits have been achieved. Increase in system performance may not be generated until a certain percentage of aircraft have the required capabilities. In order to induce a sufficient number of aircraft to equip with new capabilities and reward early investors before the required threshold is met, financial incentives may be needed. This may be offered only on a temporary basis during the initial implementation phase and may be withdrawn once a certain percentage of aircraft has equipped and improvement in the overall system performance has reached the threshold.

2.4.2  ICAO’s Policies on Charges for Airports and Air Navigation Services (Doc 9082) allow differential charges such as preferential charges, rebates, or other reductions in the charges normally payable for the use of air navigation services and facilities in a transparent and non- discriminatory manner. Charging schemes for less well equipped aircraft or rebates for better equipped aircraft could encourage earlier introduction of new on-board equipment. With the parallel and timely deployment of ground-based infrastructure upgrades, the overall ATM system capacity and efficiency could thus be improved significantly. The sooner the system performance reached the threshold level where operational benefits are substantial for better equipped aircraft, the sooner the financial/ economic incentives may no longer be needed.

2.4.3  The issue of financial incentives is complicated by the variety of governance and funding structures for ANSPs. In many cases, the ANSP must simultaneously invest in both the ground based infrastructure and controller training placing a burden on their resources that may not accommodate reductions in ANS charges done to promote equipment and training on the airborne side.

2.4.4  The FAA has developed a public-private partnerships NextGen financial incentive program under Section 221 of the FAA Modernisation and Reform Act of 2012. The Act granted authority for the Secretary of Transportation to establish an equipage incentive program to equip aircraft in the interest of achieving NextGen capabilities. Under Section 221, the Secretary may provide loan guarantees or other forms of federal credit assistance to operators of commercial and general aviation aircraft for up to 90 percent of the principal amount of loans funding such equipage. The incentive program is to be based on public-private partnership principles and is intended to leverage and maximise the use of private sector capital. The goal of the program is to encourage deployment of NextGen-capable aircraft in the National Airspace System sooner than would have occurred otherwise. Also, FAA is specifically seeking to increase the speed of adoption of base levels (equipage bundles) of NextGen equipage, which will accelerate delivery of NextGen benefits by reducing the time and expense of operations.

2.4.5 The development phase of SESAR is also a public-private partnership programme managed by the SESAR Joint Undertaking. It is developed in collaboration with the entire Air Transport Industry and supported both politically and financially by the European Commission. The coordination and implementation time-frame is crucial for the benefits of the programme as a whole, thus both public and private stakeholders need to work in partnership to ensure efficient deployment of SESAR. To stimulate the deployment phase to take place in a synchronised manner, it is crucial to develop a positive business case for each stakeholder. Financial incentives like offer loans using the public-private fund or the deployment fund, direct monetary contributions, cost reductions or subsidy for equipage upgrade, or reduce charges for ANSP services, are there to make stakeholders react and invest earlier. It also served as a purpose to discourage stakeholders to take the “last-mover advantage”, where those among the last to equip will benefit from both technology improvements and lower unit cost.

2.5 Intrinsic Advantages

2.5.1  The FAA’s NextGen Plan is to create capabilities that make air transportation safer and more reliable while increasing the capacity of airspace and reducing aviation’s environmental impact. It encompasses system upgrades like Automatic Dependent Surveillance Broadcast (ADS-B), Performance Based Routing (RNAV/RNP), Wide Area Augmentation System (WAAS) and Controller Pilot Data Link Communications (CPDLC). Each of which has its own intrinsic values beneficial to aircraft operations without massive ATC intervention.

2.5.2  ADS-B provides aircraft with traffic and weather information, it enables the determination of the best approach and routing during weather deviation. Fuel saving is possible if ADS-B route is of less track miles than the initial flight path. RNAV/RNP enables design of shorter or direct route within terminal areas with simple connections to en-route structures. Segregated arrival and departure streams are also possible with tactical design so as to reduce controller’s workload in providing radar vectors. Improved airspace capacity, increased safety due to repeatable and predictable flight paths, less fuel burn and minimize flight time means lower operational cost and less carbon dioxide emission, thus meeting both operational and environmental objectives of future ATM system.

2.5.3  WAAS/LVP improves aircraft performance with highly repeatable stabilized approach capacity, thus permits the use of more fuel efficient flight planning and approaches that have reduced weather minima. It enables greater flexibility in air traffic management with lower weather minima and more alternate airport opportunities. FANS-1A is a format of communication for CPDLC, it provides automatic position reports which requires no pilot interaction. The mixture of improvements in communication, navigation and surveillance allow ANSPs to reduce separation distance between aircraft and allow aircraft to fly their optimum routes and altitudes, thus consuming less fuel.

2.6 Future ATM operational scenarios

2.6.1  BEBS must consider System-Wide Information Management (SWIM) (A concept, introduced first by FAA in 1997, which is still in the development phase. It’s about the sharing process of the aeronautical information through all the aviation actors e.g. ATM, users, stakeholders, airport ground services etc. with the aim of increase efficiency of the system as a whole), Collaborative Decision Making (CDM) and User Prioritisation concept in a system management that might increase management complexity for ATCOs.

2.6.2  ATCOs can cope with new concepts that seek to prioritize individual aircraft only if automation is deployed at such a high level that the correct sequencing is determined before take-off or be as transparent to the ATCOs as possible and so that tactical ATC intervention remains always possible. For concepts that are based on minimum requirements to access preferable airspace, the automation requirements may be more simple.

2.6.3  Future concepts of ATM will face the need to monitor sector complexity, human capabilities and workload limitations of new systems. That is the reason why automation will be necessary to move “housekeeping tasks” to machines, permitting humans to remain “in the loop” with the correct authority.

2.6.4  As for many items related to new concepts of ATM, the responsibility and liability framework for both human and engineering actors of the system must be clearly defined.

2.6.5  ASBU (Aviation System Block Upgrades) is the ICAO programme for a step-by-step enhancement of the aviation and already considers the BEBS concept but does not state which kind of performance (navigation accuracy, fuel efficiency…) has to be considered. TBO – Trajectory Based Operations as well as PBN – Performance Based Navigation are just example of ATM operations that can create the gaps for a service priority development.

2.6.6  Any benefit coming from allowing an aircraft to fly along better routes because it has specific equipment could be negated by the tactical use of surveillance systems (e.g. radar service). In a very busy environment the only way to gain benefits from the BEBS notion is to leave aircraft flying along the BEBS routes without tactical, off-route intervention. From an economic point of view it makes no difference from the use of the surveillance system to clear traffic to direct routings. Even, the tactical use of the ground surveillance could be more efficient then leaving the traffic along the BEBS routings. This could then fill the gap between equipped and non- equipped aircraft if the non-equipped flight is permitted to fly direct track to the ground surveillance system.

2.6.7  The most suitable use of the BEBS concept is then the strategic approach. Equipped aircraft should gain advance in slot allocation and airspace accessibility.

2.6.8  Weather and equipment reliability can be other issues when BEBS routes cannot be flown. Reduced spacing airways are already under development. If aircraft flying along these routes will need to avoid weather or will move off the airway due to various reasons (technical failure, human factors…), specific automated tool and a set of rules for the pilot regarding the deviation will be needed to warn the ATCO in a prompt manner to permit immediate intervention.


3.1  The development of future ATM system requires a synchronised approach in both ground- based infrastructure upgrades and the installation of advanced technologies on-board the aircraft. “Best Equipped, Best Served” is intended to incentivise aircraft equipage of new technologies in communication, navigation, and surveillance. In order to maximise benefits to the overall ATM system and expedite aircraft equipage of these technologies, higher levels of service should be provided to aircraft with higher capabilities and performance levels.

3.2  Each of the technologies and systems has its intrinsic value. It can offer genuine benefits to the airspace users like increased safety, reduced emissions, reduced delays, and reduction in fuel used. These potential operational and economic benefits to aircraft with high equipage levels will probably not require any additional incentives.

3.3  Service prioritisation can impact mixed mode operations positively or negatively. In this case IFATCA’s policy on MMO is to be considered.

3.4  Safety and risk assessment of any service priority concept must be carried before deployment.

3.5  ATCOs should not be responsible for verifying if a user is capable to do/perform something (e.g. a request by user to perform a BEBS routing is a self-certification of capability).

3.6  Qualified or better equipped aircraft have to be easily recognised by controllers at early stage of the flight operations.

Whenever there’ll be the need to show aircraft capabilities to ATCOs then it should be presented:

  • in simple, easily recognized formats;
  • closely integrated with existing display systems;
  • maximizing the availability of equipage data;
  • minimizing the associated clutter;
  • enabling the information to be toggled on and off the display.

3.7  Service Prioritisation should rest on the following pillars:

  • Priority is determined on a strategic rather than tactical basis;
  • Collaborative Decision Making regarding Airspace Management and the required capabilities;
  • Equipage incentives, whether financial and/or operational;
  • Regulator willingness and ability to certify advanced aircraft capabilities;
  • Equitable access to airspace, viewed on a longer time scale.


It is recommended that;

4.1  IFATCA Policy is:

Service priority can be accounted to airspace users provided that:

  • Prioritisation is given in a strategic way,
  • Tactical intervention is always possible,
  • Sector Complexity does not exceed an acceptable level.

and is included in the IFATCA Technical and Professional Manual.



Federal Aviation Administration, “NextGen Implementation Plan”, 2010.

Andrew M. Churchill, Michael O. Ball, Alexander David Donaldson, R. John Hansman, “Integrating Best-Equipped Best-Served Principles in Ground Delay Programs”, Ninth USA/Europe Air Traffic Management Research and Development Seminar, ATM2011.

Gary R. Church, Aviation Management Associates, Inc., “An Achievable Approach to Implementing ‘Best Equipped, Best Served’”, The Journal of Air Traffic Control, Summer 2012.

Robert Poole, “How to Implement ‘Best-Equipped/Best-Served’”, Air Traffic Control Reform News#93, May 21, 2012.

Joseph Post, Michael Wells, James Bonn, and Patrick Ramsey, “Financial Incentives for NextGen Avionics – ADS-B Case Study”, Ninth USA/Europe Air Traffic Management Research and Development Seminar, ATM2011.

Section 221 of the FAA Modernization and Reform Act of 2012, Public-Private Partnerships (NextGen Financial Incentive Program).

Mihal Leontescu and Egija Svilane, “Incentive Mechanisms for Large Public-Private Partnerships, Empirical Evidence from SESAR”, Master Thesis within Business Administration, Jönköping International Business School, Jönköping University, 2012.

HongSeok Cho: “Understanding the impact of the potential best-equipped, best-served policies on the en-route air traffic controller performance and workload” | S.M. Aeronautics and Astronautics Massachusetts Institute of Technology, 2012.

ICAO AN-Conf/12-P/98.

Andrew M. Churchill, Michael O. Ball, Alexander David Donaldson: “Integrating best-equipped best-served principles in ground delay programs” | Ninth USA/Europe Air Traffic Management Research and Development Seminar (ATM2011).


Richard Jehlen: “Best Equipped-Best Served” (public consultation presentation) March 13, 2012.

IFATCA Technical & Professional Manual 2012.

ICAO ASBU Navigation Roadmap.

European coordination towards 12th Air Navigation Conference European Coordination presentation at ICAO ASBU Workshop (Paris 4 – 6 July 2012).

CANSO Vision 2020: Service Priority: The Next Evolution in Air Navigation Service.

IATA discussion paper and position on “Best Equipped Best Served” Airspace Operations (November 2012).

Last Update: September 30, 2020  

May 5, 2020   873   Jean-Francois Lepage    2014    

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