Kazakhstan’s air navigation service is rejecting the possibility that wake vortices from a preceding departure contributed to the aerodynamic instability of the Bek Air Fokker 100 which crashed at Almaty.

Kazaeronavigatsia insists that there was sufficient departure spacing between the Bek Air flight, departing for Nur-Sultan on 27 December, and the aircraft which had taken off immediately before.

It says both the Fokker 100 and the preceding aircraft, an Airbus A321, were classified as a medium-sized airframe – a category which includes types with a maximum take-off weight up to 136t.

Under Kazakh air traffic control regulations the minimum time interval between departures of medium-sized aircraft is 1min, says Kazaeronavigatsia.

But the interval between the A321 and the Bek Air Fokker was around 2min, it insists. “There were no violations of the time intervals during the departures of these aircraft,” it adds.

Almaty airport’s president indicates that the spacing between the two aircraft was 1min 52s.

Preliminary evidence from Bek Air and surveillance video indicates that the aircraft struggled to climb after rotating, experiencing instability during lift-off before striking the ground and veering into structures.

“[Take-off] intervals established in [Kazakhstan] comply with global requirements and standards,” says Kazeronavigatsia. “All international airports have similar intervals between take-offs and landings of aircraft.”