A Royal Air Force pilot and navigator were killed when their fighter jet slammed into a remote Scottish hillside during a training exercise, officials said.

Another Tornado F3 involved in the same exercise returned to the base, RAF Leuchars in eastern Scotland north of Edinburgh, The Aberdeen Press and Journal reported Friday.

The jets were flying through Glen Kinglas, a remote valley in Argyll in western Scotland, shortly before noon Thursday when the crash occurred at an area named Rest and Be Thankful. Witnesses said both jets appeared to be flying low.

"They were very, very low just above the tree line," Morag Campbell, a local resident, told the newspaper. "There was a terrible noise after they flew up the Rest and Be Thankful and we both said at the time that it sounded like one of them had crashed."

Sgt. Tim Sugars of the RAF mountain rescue team, which was sent to the crash site, said the impact sent burning debris over the area, with some of it hitting the A83, a road connecting the area with central Scotland. No one on the ground was injured.