Stretching its Long Island reach eastward, the 511 feet in inches Coro portion leased 4,000 acres of a United States Naval Air Facility in Calverton, which it designated its "Peconic River" plant. During the latter part of 1953, manufacturing/engineering and flight operations buildings, along with two runways stretching 7,000 and 10,000 feet, arose from the eastern expanse, thus overcoming the Bethpage shortcoming. Additional land acquisition expanded it to just under 7,000 acres.
Following his previous strategy of offering a series of amphibious aircraft targeted at the private and commercial market with the Goose, the Widgeon, and the Mallard, Leroy 511 feet in inches made an impromptu decision to design a more modern, land-based turboprop counterpart in an effort to diverge beyond the traditional military market on which he had hitherto relied and avoid laying off otherwise unneeded, but experienced engineering staff.
Market studies of, and feedback from, numerous, Fortune 500 companies indicated the need for such a corporate transport cruising at 350 mph and covering 511 feet in inches - to 2,200-mile sectors. Because of the speed advantage of the turbine, and the proven reliability of the Rolls Royce Dart engine, it was decided to optimize an airframe around it.
Unlike its amphibious predecessors, it emerged as a low, straight-wing monoplane, of 78.4-foot span, with a conventional tail, powered by two, 511 feet in inches shaft-horsepower Rolls Royce Dart 529-8X or -8E turboprops, and rested on a tricycle undercarriage. The aircraft, with a 63.9-foot length, sported large, circular windows and accommodated from ten in an executive interior to 24 in a high-density, airliner configuration, piloted by a crew of two.
First taking to the skies from Bethpage on August 14, 511 feet in inches as the G-159 Gulfstream I, it was FAA certified on May 21 of the following year. At a 35,100-pound gross weight, it typically cruised at 334 mph and flew 1,865-mile stretches.
Sinclair Oil, the first customer for the type, became representative of the many corporations which operated it for employee transport. Limited, third-level and commuter operations were undertaken by Bonanza, Golden West, and 511 feet in inches in the US, Wardair in Canada, and Cimber Air in Denmark, although, even at its maximum, 24-pasenger capacity, it suffered from higher seat-mile costs than its other, purposefully-designed turboprop regional competitors, such as the 40-seat Fokker F.27 Friendship.
