Achievements

/ Achievemnts

Free Route

Progressive implementation of Free Route Airspace across South-East Europe, led by DANUBE FAB, has enabled 24/7 trajectory-based operations in six States, forming one of Europe’s most extensive and integrated cross-border FRA environments.

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Cross-Border Sectors

The two partner States of Romania and Bulgaria implemented two cross-border sectors on 11 December 2014, the first time that cross-border sectors have been implemented under a FAB framework

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Technical Rationalisation

Through coordinated procurement, shared infrastructure, and harmonised procedures, DANUBE FAB strengthens technical interoperability and operational efficiency, supporting seamless service provision and alignment with SES and SESAR objectives.

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Free Route

DANUBE FAB has played a key role in the progressive implementation of Free Route Airspace (FRA) in South-East Europe. FRA enables airspace users to plan and fly preferred trajectories without the constraints of a fixed route network, contributing to improved flight efficiency and reduced environmental impact.

Implementation timeline:
  • October 2013 – Night-time FRA implemented nationally in Romania and Bulgaria.
  • August 2015 – Cross-border night FRA established between Romania and Hungary (Inter-FAB).
  • March 2017 – Night FRA extended to include Romania, Bulgaria, and Hungary.
  • December 2018 – Slovakia joined the night FRA operations.
  • November 2019 – 24-hour FRA implemented in Romania, Bulgaria, and Hungary; Slovakia continued night FRA.
  • January 2021 – Slovakia transitioned to 24-hour FRA.
  • February 2022 – Republic of Moldova joined 24-hour FRA; cross-border interface with Baltic FRA established via Slovakia.
  • February 2023 – Czech Republic joined 24-hour FRA. FRA is now operational 24/7 across Romania, Bulgaria, Hungary, Slovakia, Republic of Moldova, and Czech Republic.
Together with its regional partners, DANUBE FAB supports the development of South-East Europe Free Route Airspace (SEE FRA)—one of the largest cross-border FRA blocks in Europe.

Cross-Border Sectors

On 11 December 2014, DANUBE FAB became the first Functional Airspace Block to implement cross-border sectors (CBS), redefining sector boundaries based on operational needs rather than national borders. This pioneering initiative enhances flight efficiency, airspace capacity, and safety, while reducing environmental impact.

Two cross-border sectors were established:
  • Sector DF 1 – Controlled by BULATSA over Romanian territory. It allows more efficient traffic management around a newly established military area and enables optimised descent profiles into Varna and Burgas airports.
  • Sector DF 2 – Controlled by ROMATSA over Bulgarian territory. It improves coordination near restricted areas and reduces manual control transfers, particularly for westbound traffic traversing complex border contours.
Both sectors are operational 24/7 above FL245. In each case, air traffic services, communication, and surveillance are provided by the cross-border ANSP, while navigation, meteorological, and aeronautical information services remain under the responsibility of the territorial ANSP.

Key operational and environmental benefits include:
  • More direct routings, reducing fuel consumption and emissions
  • Enhanced conflict resolution within single sectors, reducing coordination workload
  • Optimised descent profiles into terminal areas
  • Reduction in controller workload and manual coordination steps

Strategic and governance aspects:
  • A legal and institutional framework was developed, including a Joint Designation Act and updated charging zone boundaries.
  • Issues of liability, civil-military coordination, insurance, and search and rescue responsibilities were resolved through bilateral agreements.
  • Operational procedures were harmonised, and service level agreements were established for CNS infrastructure usage.

This achievement demonstrates the high level of trust, cooperation, and institutional maturity within DANUBE FAB and serves as a replicable model for other FABs across Europe seeking to implement cross-border service provision in line with Single European Sky objectives.

Technical Rationalisation

DANUBE FAB has undertaken a wide range of technical and operational initiatives aimed at improving interoperability, efficiency, and cost-effectiveness through joint planning, procurement, and harmonisation.
Key achievements include:

Joint Procurement and Infrastructure Sharing
The two ANSPs have successfully coordinated common procurement actions, such as the Voice over IP communication system, and continue to explore new opportunities for shared technical systems and services. Agreements on radar and DME data exchange allowed the optimisation of surveillance and navigation infrastructure, avoiding redundant investments.

Common Training Framework
A shared training framework has been developed for ATCOs, ATSEPs, and MET staff. It includes harmonised selection criteria, joint training materials, and mutual recognition of training modules, with implementation monitored by the Common Training Board.

Extended OLDI Implementation
A comprehensive set of OLDI messages is implemented across both ACCs, enhancing ground-ground coordination and supporting the goal of seamless ATC operations across the FAB. Continuous monitoring and updates ensure alignment with evolving standards.

Service Level Agreements (SLAs)
Bilateral SLAs have been established and maintained for the shared use of communication, navigation, and surveillance infrastructure, ensuring interoperability and continuity of service.

Under the dedicated implementation project "Technical Rationalisation and Infrastructure", DANUBE FAB carries out activities such as the review of existing CNS strategies, development of new technical projects based on strategic impact studies, and participation in initiatives like NewPENS migration, D-ATIS, GBAS implementation, and WAM data sharing.


These efforts contribute to enhanced interoperability, reduced procurement costs, and better integration with European initiatives under SES and SESAR.

Funding and Support

DANUBE FAB has benefited from European Union financial support and continues to explore co-funding opportunities for cross-border initiatives contributing to the objectives of the Single European Sky.

Key aspects:

EU Funding Support
During the development and implementation phases, DANUBE FAB received financial support from the TEN-T programme for activities including operational simulations, communications campaigns, and strategic studies. Public acknowledgement of EU funding was ensured in line with Article III.2.3 of the related grant decisions

SESAR Engagement
DANUBE FAB, through BULATSA and ROMATSA, actively participates in SESAR 3 Joint Undertaking projects. Ongoing and planned initiatives are coordinated to seek funding under the SESAR Digital Sky Demonstrator calls and future deployment instruments.

Joint Procurement Efficiency
The FAB has leveraged joint procurement for selected CNS systems and studies, improving cost-effectiveness and increasing competitiveness in funding applications.

Business Case Justification
Independent cost-benefit analyses (CBA) confirmed the value of investment in DANUBE FAB initiatives. For example, FAB-wide airspace optimisation has led to long-term savings for both ANSPs and airspace users, supporting further funding eligibility.

Future Prospects
DANUBE FAB continues to monitor and engage with EU financing frameworks such as the Connecting Europe Facility (CEF) and future instruments supporting Green Deal and Digital Europe objectives. Funding strategies are aligned with the FAB’s implementation projects and performance targets.

Lessons learned

The implementation and evolution of DANUBE FAB have provided a number of valuable lessons relevant to cross-border cooperation in air traffic management:

A long-term strategic vision is essential.
Functional Airspace Blocks require continuity and strategic commitment over time to deliver tangible operational and performance benefits.

Stakeholder engagement takes time.
All actors—civil and military, operational and institutional—require sufficient time to evaluate the feasibility, implications, and benefits of joint initiatives.

Support at European level is critical.
The development of innovative cross-border projects benefits from clear guidance, political endorsement, and financial support under EU programmes.

Geographic proximity and shared airspace characteristics enhance success.
Projects involving cross-border air traffic services, Free Route Airspace, and CNS rationalisation are most effective where operational needs are closely aligned.

Proactive project management is key.
A hands-on, structured approach to planning and execution supports the identification of common priorities and fosters a results-oriented FAB culture.

Effective communication and mutual understanding matter.
Close cooperation, transparency, and awareness of national organisational cultures enhance decision-making and implementation at all levels.

Safety is the overriding priority.
All joint activities must be driven by a shared commitment to maintaining and enhancing the highest levels of safety.

The social dimension must not be overlooked.
Continuous dialogue with professional organisations and staff representatives is essential to ensure smooth implementation and lasting acceptance of cross-border arrangements.

These lessons underpin the continued development of DANUBE FAB and are relevant to future initiatives under the Single European Sky framework.

Inter-FAB Cooperation

DANUBE FAB actively participates in the InterFAB Coordination Platform, a collaborative initiative among the nine Functional Airspace Blocks (FABs) aimed at enhancing coordination and reducing fragmentation within the European Air Traffic Management (ATM) network. Through this platform, DANUBE FAB contributes to aligning common goals, sharing best practices, and strengthening the collective voice of FABs in the context of the Single European Sky (SES) framework.

Key areas of InterFAB cooperation include:
  • Operational Coordination: Efforts to optimize airspace interfaces, including cross-border Free Route Airspace (FRA) implementations and harmonized sector configurations.
  • Performance Enhancement: Joint activities focused on improving aggregated performance metrics, supporting SES objectives, and facilitating cooperation with the European Commission.
  • Communication Strategies: Development of unified communication approaches to effectively convey the role and achievements of FABs within the broader European ATM landscape.
  • Research and Innovation: Participation in workshops and studies addressing topics such as traffic predictability, environmental impact, and the integration of new technologies into ATM systems.
DANUBE FAB's involvement in InterFAB initiatives underscores its commitment to collaborative progress and continuous improvement in European airspace management.

Funding and Support

Through EU co-funding and strategic participation in SESAR initiatives, DANUBE FAB advances cross-border projects that support the goals of the Single European Sky and long-term operational efficiency.

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Lessons learned

Through its development, DANUBE FAB has identified key lessons for successful cross-border cooperation—emphasising long-term vision, stakeholder engagement, EU-level support, and the primacy of safety in delivering lasting results within the Single European Sky framework.

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Inter-FAB Cooperation

Through the InterFAB platform, DANUBE FAB contributes to aligning common goals, sharing best practices, and reinforcing the collective voice of FABs within the Single European Sky framework.

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