Why a properly authorised and digitally coordinated flight may still be exposed to an aircraft that never appears on the operator’s screen writes Manuel Ignacio Pérez Pan There is a reassuring moment during the preparation of a beyond visual line of sight (BVLOS) flight when everything appears to be in place. The operational volume has

There is a reassuring moment during the preparation of a beyond visual line of sight (BVLOS) flight when everything appears to be in place. The operational volume has been defined, the airspace has been reviewed, the required authorisations have been obtained and the relevant notifications have been issued. The planned flight may be visible within a UAS traffic management (UTM)/ U-space or flight-management environment, alongside the cooperative traffic information available to the operator.

It is easy, at that point, to feel that the airspace conflict has been managed.

Operationally, however, what has been achieved is more specific. The probability of an encounter has been reduced through planning, coordination and the exchange of available information. That is valuable, but it is not the same as having the means to detect and resolve every conflict that may still develop after take-off.

This distinction sits at the centre of the air-risk model contained in the European Union Aviation Safety Agency (EASA) EASA Easy Access Rules for Unmanned Aircraft Systems. Strategic mitigations act before the flight by reducing encounter rates or limiting the period during which the UAS is exposed to other traffic. Tactical mitigations are applied after take-off to address the residual collision risk that remains.

The terminology must be handled carefully. EASA explicitly warns that the SORA concept of “tactical mitigation” should not be confused with the formal provision of tactical separation services described in ICAO’s air traffic management framework. The title of this article is therefore not intended to suggest that every BVLOS operation requires an air traffic separation service. It draws attention to a more fundamental point: pre-flight deconfliction cannot, on its own, resolve an airborne conflict in real time.

In practical BVLOS operations, especially those conducted at very low level or along extended infrastructure corridors, the difference is far from academic. A flight may be correctly authorised and strategically coordinated while remaining exposed to an aircraft that is absent from the information available to the remote crew.

The strategic layer may have worked exactly as intended. The tactical problem can still remain.