The ndege yakabhururuka muna April 1937, richisvika 340 mph (550 km / h) pa 20,000 ft (6,100 m). Kunyange zvazvo turbo-supercharger akanga zvikuru isingavimbiki uye maonero kubva mutyairi wendege pamusoro yasimuka uye kumhara akanga chaizvoizvo nonexistent, USAAC akanga avimbiswa zvakakwana intrigued nokuda 13 turbocharged ndege kuti bvunzo basa YP-37s uye akaramba imwe ndege kutiza muna June 1939. Curtiss XP-37, ndege akashandisa yepakutanga Model 75 airframe pamwe radiators akatasva kurutivi fuselage kumativi injini. Cockpit akaendeswa kure nechekumashure kuti nzvimbo kuti radiators uye turky bulbocharger hurongwa, uye kuti ndege nepakati.
Muna 1939