North Korea has been forced to ground a fleet of Soviet-era military planes because of the high oil price, South Korea's Yonhap news agency reported.
The Antonov An-2 transport first flew in 1947
Fuel is being diverted for other training flights, Yonhap quoted a military source as saying.
The Antonov An-2 biplanes - of which North Korea's air force is thought to have about 300 - are able to drop special forces behind enemy lines.
The planes, which can cruise below radar, carry some 12 soldiers.
North Korea's impoverished economy has suffered from energy shortages for years, and rising oil prices have made the situation worse.
The Antonov, designed and built in the Soviet Union, first flew in 1947, and is still used by a number of military and civilian operators around the world.
The plane is useful in special forces operations because of its extremely low minimum speed - it can fly as slowly as 48km/h (30mph) without stalling, according to aviation experts.
North Korea's air force fields hundreds of aircraft, but the vast majority are ageing Soviet models - such as the MiG 21 fighter - or Chinese copies outclassed by more modern aircraft fielded by the US, South Korea or Japan.
North and South Korea are still technically at war as a peace accord to bring an end to the 1950-53 conflict has never been signed.