Two RAF air crew died when their Tornado jet crashed in Argyllshire.
The Ministry of Defence, in confirming the fatalities late on Thursday afternoon, said next of kin have been informed.
Emergency officials on the scene said there were few remains of the Tornado F3, based in RAF Leuchars in Fife.
The jet slammed midway up a hill in Glen Kinglas during a routine training flight, emergency officials said.
The pilot and weapons systems operator on board have yet to be named.
An emergency services official said there was "little to see" from the wreckage which was described as scattered "over a sizeable area".
An MoD spokesman said: "It is with deep regret that the Ministry of Defence must confirm the deaths of two RAF air crew from 43 Squadron, RAF Leuchars, in a Tornado F3 crash today.
"The aircraft crashed during a routine training flight at 11.45am at Glen Kinglas in Argyll.
"The next of kin have been informed and have requested a period of 24 hours grace before further details are released."
The crash happened close to the Rest And Be Thankful tourist spot near the village of Arrochar on the A83, about 45 miles north-west of Glasgow.
Search and rescue helicopters from the HMS Gannett naval base and RAF Lossiemouth were scrambled to search the remote countryside for the wreckage and the crew.
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Sergeant Tim Sugars, from the RAF mountain rescue team, said units from Kinloss and Leuchars were at the scene. He said the jet crashed at speed, with wreckage spread out over a considerable area. Two firefighters were airlifted to the crash scene to put out smoldering wreckage.
No civilians are thought to have been hurt in the accident.
Air accident investigators will also be attending in a bid to establish the cause of the crash.
RAF Squadron Leader Paul Lipscomb would not speculate on the fate of the crew members.
He said: "At the moment the families have not been informed and it would be wrong for me to continue talking on this subject."
He confirmed that the training exercise had involved two aircraft and the other plane had returned safely to the RAF base.
He said the clear-up operation would take a number of days.
Weather in the area at the time was said to be overcast with thick cloud.
Roads are closed near the crash scene
Witnesses said planes appeared to have been flying much lower than usual.
Andy Graham, 60, a retired rigger who moved to Arrochar three years ago, said he saw two Tornados flying low in the area around lunchtime.
He said: "We get jets flying over here on training exercises quite regularly. It's not unusual to see them and you definitely hear them.
"But today they seemed to be flying much lower than normal. "We watched them fly along the loch, up through the glen and towards the Rest And Be Thankful."
RAF Leuchars is home to two Tornado Squadrons - 111 Squadron and 43 Squadron. They operate the Tornado F3 aircraft, which has a crew of two, a pilot and a weapons system officer who controls the radar, missiles and defence systems. Both Leuchars squadrons saw action in Iraq - in 1991 in the Gulf War, and in 2003 in Operation Telic.
The F3 came into service with the RAF in the 1980s.
The pilot in the front seat flies the aircraft while the rear seat weapons systems officer controls the radar and defensive countermeasures systems.
