Formation Flight and Formation Like Flying Involve Collision Risk. Procedures must Be Agreed before Flight and Followed Continuously

Two helicopters en route from Tallinn, Estonia, to Piikajärvi, Finland, collided mid-air near Eura aerodrome on May 17, 2025 and crashed to the ground. They were destroyed, and all five occupants sustained fatal injuries.

The cause of the accident was traced to human factors, as the examination of the wreckages revealed no technical anomalies.

“The helicopters proceeded in a formation-like arrangement during the en-route phase of the flight. Because formation flying and formation like flying involve a collision risk, applicable procedures are agreed on before flight, and they are observed carefully,” states investigator-in-charge Janne Kotiranta.

“Separation between the helicopters was relatively small, yet it did not remain constant. Just before reaching the Eura aerodrome, the relative position of the helicopters changed and they closed in on each other at an angle that hampered each pilot’s ability to observe maneuvers of the other aircraft, and the pilots were also unaware of each other’s intentions,” explains Kotiranta.

The Safety Investigation Authority, Finland (SIAF) recommends taking action to increase the knowledge of formation flying in general aviation and extending the requirements contained in recent emergency locator transmitter standards to helicopters used for general aviation.

“Investigation indicated that the on-board emergency locator transmitters mounted in the helicopters did not activate. Even though this failure would not have been a survival factor in the investigated accident, the finding is alarming,” states Kotiranta.

The Bureau of Enquiry and Analysis for Civil Aviation Safety of France (BEA) assisted the SIAF in downloading of data from avionic equipment because the SIAF does not have a laboratory for the purpose. Retrieved data helped to determine flight path details as well as helicopter parameters and maneuvers during the moments preceding the collision.

Link to summary and investigation report

Link to press release in Estonian

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