Passengers wait at the airport in Hanover on December 29, 2018 after a security incident resuled in flight operations been suspended when a man broke through a gate with a auto before being stopped by Police.
Police stopped him after several hundred metres, it said.
Federal police were investigating whether the driver was mentally disturbed, under the influence of drugs, trying to carry out an attack or drove through the perimeter for some other reason, German news agency dpa reported.
Bomb disposal experts were examining the auto. No one was hurt.
The 21-year-old suspect's motive remained unclear on Sunday, but police said they still had no indication his alleged actions were terror-related. "A man broke a barrier with a vehicle and went on the tarmac", Hanover police posted to Twitter.
The man was believed to have acted alone. They found no traces of explosives, and flight operations resumed shortly after 8 p.m. - about 4 1/2 hours after the man drove onto the airfield.
Hanover police said the driver had tested positive for cocaine and amphetamines. Police said they couldn't give further information on where he came from because he wasn't carrying an identity card.
'Arriving flights are diverting, departures have been suspended after a vehicle driver reportedly tried to enter the apron.
Incoming flights were being diverted to other airports.
Hannover Airport (HAJ) is the ninth-largest airport in Germany, handling 5.8 million passengers in 2017.