Two prototypes were built, one of which is still (as of August 2003) preserved in the USAF Air Museum.
This tiny aircraft was only 1.64m wide, 3.25m high and 4.53m long, with a wing span (unfolded) of 6.44m. It was considered to be extremely ugly. Fitted with a Westinghouse J34-WE-7 turbojet capable of 1360kg static thrust it achieved a maximum speed of 580km/h in level flight, well below its intended design speed of 1068km/h.
Further development ceased when more conventional fighters with considerably improved overall performance became available to defend bombers. All tests undertaken on the XF85 were carried out using a Boeing B29 Superfortress bomber because a prototype B36 was unavailable. Later, a B36 was used as a mother ship for similar tests, carrying a conventional Republic F84F Thunderstream fighter. These tests, known as FICON (Fighter-in-Convair) experiments, were also found to be of little long term practical use and the whole concept was dropped.