Police said the single-engine propeller plane plunged to the ground early today afternoon shortly after taking off from an airfield at Hatten, near the city of Oldenburg.
The plane came down at the side of the A28 highway, with one wing hitting the autobahn's emergency lane, but no one on the ground was hurt.
Police say the 69-year-old pilot died at the scene. The three passengers, two men and a woman, suffered life-threatening injuries.
The cause of the crash was not immediately clear.