“Most of the control towers at the airfields and watchtowers from that period have been demolished now, they are at great risk,” Keay told BBC Radio 4.
“It was built during the Battle of Britain and it is abandoned and incredibly fragile. It is at risk if action is not taken.”
Following investigation, The Landmark Trust identified 20th century military structures as a vulnerable category of construction.
Keay added: “If we don’t take care of them and decide we want to keep them, we’re going to lose them.”
Ibsley is expected to be converted into a four-bedroom holiday home with a first-floor kitchen and dining room with a 180-degree view into the former control room.
The charity intends to restore it to its original art deco form designed by British architect Edward Luchins.
Keay said: “We intend to bring it back to how it was in the war, to revive the spirit and aesthetic of that period, with a modern twist.”
It is the last completed building on the airfield and, pending fundraising for charity, will be given a new lease of life.
Originally the airfield was intended to act as a satellite station for RAF Middle Wallop in Hampshire, but it eventually became a fighter command station in its own right.
The airfield was operational between 1941 and 1944 and when its military use ended, it served as an automobile racing track in the 1950s.