Dutch investigators have opened an inquiry after a KLM Boeing 737-300 took off from a taxiway at Amsterdam Schiphol two days ago.
The aircraft, registered PH-BDP, was departing on a service to Warsaw when the incident occurred.
Flight KL1369 was supposed to use runway 36C but instead took off from taxiway B which runs parallel on the eastern side.
A spokeswoman for the Dutch Safety Board states that the incident is being classified as "serious" by the investigators.
The aircraft continue to Warsaw and the crew was interviewed on return, she adds.
KLM lists KL1369's scheduled departure time as 20:20 and the spokesman says the incident took place at 20:36.
Amsterdam Schiphol would have been in darkness at this time. Meteorological data from the airport shows good visibility and weather conditions at the time.