Wreckage was found near the summit of Ben Macdhui
An air traffic controller lulled two US fighter pilots into a "false state of security" before their planes crashed into a mountain in 2001, a court martial has heard.
Group Captain Alistair McGrigor, for the Crown, said Flight Lieutenant Malcolm Williams was not solely responsible for the tragedy.
But by advising the F15s to descend to 4,000 ft - 2,500 ft below the safety altitude - Flt Lt Williams formed a "direct causal link to the impact", Group Captain McGrigor said.
Flt Lt Williams has been charged with causing the deaths of Lieutenant Colonel Kenneth Hyvonen, 40, and Captain Kirk Jones, 27, by telling them to descend to 4,000ft when the minimum safety altitude in the area was 6,500ft.
He faces an alternative charge of negligently performing in his duties which involved providing radar information to the pilots.
The controller has pleaded not guilty to all charges.
The jets crashed into Ben Macdui in the Cairngorms during a snowstorm in March 2001.
Group Captain McGrigor was delivering his closing speech to a jury of six senior RAF officers, assisted by a judge advocate, on the 18th day of the hearing.
Captain Kirk Jones died in the accident
He said: "He (Flt Lt Williams) created a false environment and lulled the air crew into a false state of security which ultimately led to the fatal impact."
Group Captain McGrigor said Flt Lt Williams' actions were a "direct causal link" to the impact.
He said: "Under radar information service,
pilots can accept or reject what they are told, but the Crown says they are entitled to believe that what they are told is safe.
"A descent to the safety altitude of 6,500 ft was the only proper response. Flt Lt
Williams was just plain wrong."
He said Flt Lt Williams' reaction when the jets disappeared from radar was "a powerful piece of evidence".
"Flt Lt Williams' gut reaction is indicative of an experienced air traffic controller replaying the exchange over in his mind like a video and realising that something has gone horribly wrong."
He is due to conclude his closing speech this afternoon, before Michael Jones QC delivers his speech for the defence.