French investigators have disclosed that they are probing a substantial loss of altitude by an Air Algerie Boeing 737-800 during a go-around at Paris Orly last month.
The aircraft, arriving from Tlemcen in north-western Algeria on 6 December, had been established on the localiser of runway 25.
French investigation authority BEA says an airport bird-control vehicle had approached the runway from taxiway W33, which intersects about 800m from the threshold.
Although the vehicle came to a halt at the edge of the runway, an incursion alert was triggered while the 737 was on short final.
The controller ordered the aircraft to abort the approach and execute a go-around.
BEA says the aircraft climbed along the runway centreline to 2,000ft and commenced a left turn.
But while the jet progressed with the turn, the inquiry says, it lost altitude and descended to 1,250ft before climbing again to 3,000ft.
Meteorological data for Paris Orly at the time indicates reduced visibility as a result of rain and mist.
BEA says the crew conducted another approach and landed without further incident. None of those on board was injured and the aircraft (7T-VJM) was undamaged.
Cirium fleets data shows the twinjet was originally delivered to the Algerian flag-carrier in 2000.