Four people died in the accident involving a light aircraft and a helicopter near Waddesdon, police have revealed.
In a statement released by Thames a Valley Police tonight, they said the accident was reported shortly after noon.
"Officers and members of the other emergency services including the fire and ambulance services attended the scene," the statement said.
"A light aircraft and a helicopter were located in woodland at Upper Winchendon. We can now sadly confirm that four people have died at the scene."
Superintendent Rebecca Mears, said, “Officers are in the process of working to locate and support their next of kin. The Air Accidents Investigation Branch, the AAIB, has been informed and their staff have been on the scene.
“These are the early stages of the investigation however Thames Valley Police will continue to work closely with investigators as they establish the circumstances.”