Registered as an Interstate S-1B1. The aircraft is painted as USAAF serial "432554" but was built as Interstate L-6 Grasshopper serial 43-2635; serial 44-32554 was a Bell P-39Q Airacobra originally earmarked for the RAF but was diverted to the USSR.

Registered as an Interstate S-1B1. The aircraft is painted as USAAF serial "432554" but was built as Interstate L-6 Grasshopper serial 43-2635; serial 44-32554 was a Bell P-39Q Airacobra originally earmarked for the RAF but was diverted to the USSR.

When the US entered WWII, the USAAF contracted with Interstate for 250 S-1B aircraft, designating the prototype as the XO-63. It was the last aeroplane to use the 'O' (for observation) designation, later the production planes were re-designated L-6s. However, the aircraft had significant overheating problems that were only partially solved and had the dubious distinction that fewer L-6s were built than any other USAAF liaison/utility aircraft. This example is on display at the National Museum of the USAF.