At around 6pm, a Finnair pilot radioed in to the control tower at Hamburg airport that he had spotted the drone at a height of around 250 metres, passing just 30 metres away from his Embraer E190 aircraft, which has a capacity of 80 passengers and four crew.
Air traffic controllers at the tower immediately warned the police, who searched the area where the drone was believed to have taken off but found nothing that could lead them to the pilot.
Now they are investigating on suspicion of a dangerous intervention into air traffic.
Hamburg is one of several German states which have introduced extra controls on the use of drones.
No flying is allowed within a 1,500-metre radius of the airports at Fuhlsbüttel and Finkenwerder – whether drones, kites or balloons.
And because many flight paths pass over the city centre, prospective drone pilots need permission to fly from the German Air Safety Authority (Deutsche Flugsicherung) outside these controlled areas if they plan to take their machine above 50 metres.