Saif Omer, Air West's managing director, said the lone hijacker walked out of the aircraft after it landed in Chad and said he wanted asylum in Britain. Nobody was injured, he said.
The man had been holding a pistol to the pilot's head during the flight, Omer said.
Air West 612 took off from Khartoum, Sudan, for the western city of Al-Fasher when the pilot was forced to change direction to Chad, said Khartoum's airport manager, Yussuf Ibrahim.
Air West, based in Khartoum, is a privately owned company, and operates domestic passenger services and international cargo charters.
It is one of 95 airlines banned from landing at European airports because of its safety record.
It was not clear how the hijacker got on board the craft with a weapon, but Sudanese security is often lax, especially on internal flights.