Sikorsky S-51 NX19800 prototype in flight between Bridgeport and East Hartford, Connectitcut Published on February 15, 2013 in 16 February 1946Full resolution (749 × 419) ← Previous Next → The prototype Sikorsky S-51 commercial helicopter, NX19800, in flight between Bridgeport and East Hartford, Connecticut, 1946. (Sikorsky Historical Archive)