4D Skyways

Improving trajectory management for European air transport

The SESAR Horizon 2020 4DSkyways project (PJ18 Wave 2) validated SESAR Solutions for Trajectory Based Operations (TBO) in the tactical execution phase for en-route and TMA operations. The project performed twenty-one validation exercises, delivered five data packs, and progressed the maturity level of all its solutions.


The main objectives of PJ18-W2 and its solutions are as follows:

  • Validating improvements to the ground trajectory prediction and separation management/ monitoring tools by using aircraft trajectory data, more precise weather data, improved algorithms and machine learning techniques. This decreases trajectory uncertainty and thus reduces ATCO workload and increase airspace capacity (#53A and #53B).
  • Validating complex Controller-Pilot Data Link Communications (CPDLC) clearances sent in advance of the horizontal, vertical, and longitudinal trajectory change to enhance the synchronisation of the airborne trajectory with the ground trajectory. Automation keeps the flight crew and the ATCO workload to a low level. It additionally decreases trajectory uncertainty and increases airspace capacity (#56).
  • Exploring the augmented automation capabilities on the aircraft through a new concept, which should improve the situation awareness of the aircrew and allow longer-term anticipation. Investigating how the benefits and impact of increased levels of automation in ground ATC tasks could be measured (#57).
  • Defining a trajectory common service as an alternative architecture for trajectory exchanges between ground ATM actors compared to the current European ATM fragmented approach to improve its cost effectiveness (#88).
  • Publishing a Trajectory Management Document describes the integrated picture for trajectory management developments (including Flight & Flow Information for a Collaborative Environment - FF-ICE) and outcomes. A key aim was to provide an accessible and readable document, suitable for stakeholders that might not be familiar with typical SESAR documents.


The project designs, develops and validates trajectory management improvements which aim to increase airspace capacity, and fuel efficiency and safety.


EUROCONTROL is the overall project manager for the 4D Skyways project and the solution leader for Solution 56.

We contribute:

  • operational, technical, architecture and validation expertise in the field of ATM operations;
  • project management and grant management expertise related to large-scale projects involving multiple international partners;
  • the ESCAPE and IDEAS platforms at the EUROCONTROL Innovation Hub.

4DSkyways Project Deliverables

The main project deliverables take the form of SESAR Solution data packs which typically contain:

  • Safety and Performance Requirements - INTEROPerability requirements (SPR-INTEROP)/ Operational Service and Environment Definition (OSED);
  • Technical specification (TS)/Interface requirements specification (IRS) (when relevant, this includes documentation (SDD) of the services which are enabled by the SESAR Solution or common services);
  • Cost benefit analysis (CBA);
  • Validation report (VALR).

In addition, the Trajectory Management Document provides an integrated view of SESAR Trajectory Based Operations in a single document.

How to read the 4DSkyways deliverables?

Depending on what you would like to get out of the deliverables, we recommend a different approach to reading them.

  1. You'd like a brief introduction to 4DSkyways and the main results? We recommend that you read the executive summaries and the main conclusions and recommendations in section 5 of the validation reports.
  2. You'd like to have a better understanding of the TBO use cases with a higher maturity and that are targeting industrialisation and deployment? We recommend that you read the Trajectory Management Document for an overall view, and then focus on the Solution #53B and #56 deliverables.
  3. You're a TBO fanatic and keen to learn as much as possible about our work? Enjoy browsing through all of the deliverables.

What our video about a PJ18 simulation at EUROCONTROL