The Conroy Turbo Three was a series of two Douglas DC-3s modified with turboprop engines by Conroy Aircraft. The first conversion first flew on May 13, 1969. Two Rolls Royce Dart Mk. 510 engines from a crashed Vickers Viscount previously operated by United Airlines were used to replace the original Pratt & Whitney radial engines. The replacement engines increased the aircraft's cruising speed from 170 mph to 215 mph.