Seven air force personnel were killed when their aircraft crashed in central Thailand on Wednesday, an air force spokesman said.
Capt Monthon Suchakorn said the aircraft banked sharply shortly after take-off, hit the ground and exploded, shattering the plane into small pieces. All aboard were killed.
The crash occurred in Nakhon Sawan, about 210 kilometres north of Bangkok.
"This is the biggest loss for the air force in recent years," Capt Monthon told reporters.
The Learjet, which had been in service for 18 years, was on an aerial photography mission from an airfield in Nakhon Sawan, the spokesman said.
"The aircraft was taking off when the nose went down and when it exploded it was shattered into small pieces," he said.
An air force team will investigate the accident, he said.