This was the first Boeing 747SP to be constructed and therefore could be considered to the the 747SP prototype. The order for ten B-747SPs was jointly announced by Boeing and Pan American on September 10, 1973 subject to satisfactory financing arrangements being made. The cost of each airframe was calculated to be some $US 28 million with delivery of the first aircraft to take place in early 1976.

Major assembly commenced at the Everett Plant of the two wing sections on November 05, 1974, but major sub-assemblies and component manufacture had already started with the many Boeing subcontractors prior to this date. The completed airframe was rolled out at the Everett plant in the Boeing red-white-blue house colours and marked as 'N530PA' with Pratt & Whitney JT9D-7A engines on May 19, 1975 in front of many hundreds of Boeing employees and invited guests. It was parked next to the original Boeing 747 to emphasize the reduced body length of this new member of the Boeing 747 family.

It was entered onto the United States Aircraft Register as N747SP on June 27, 1975 and flew for the first time on July 04, 1975. It was equipped with an extensive array of electronic equipment that was required to record and process flight test data needed to satisfy F.A.A. requirements for the granting of its Type Certificate. The flight crew for this historic flight were Captain Jack Waddell, Boeing's Chief Test Pilot, Captain Lew Wallick, Boeing's Director of Flight Operations who occupied the right hand seat and Kenneth R. Storms who was the Flight Engineer.

Having completed test and certification flying the aircraft was returned to the Boeing factory to have the flight test equipment removed and the cabin refurbished in preparation for handing over to Pan Am.

Reregistered as N530PA it was the third 747SP to be delivered to Pan Am when it was handed over on April 26, 1976 named 'Clipper Mayflower'. This name was chosen to reflect the spirit of the upcoming bicentennial celebrations.

In April 1985 Pan Am sold its entire Pacific Division (routes and aircraft) to United Airlines for $US 750,000,000 in an attempt to overcome its dire financial problems. Ownership of 'Clipper Mayflower' was officially transferred to United Airlines on February 11, 1986. Retaining its current registration it entered United service with the existing Pan Am cheatline and an all-white tail. It was reregistered as N140UA on July 01, 1986. By September 1987 it had been repainted in the United 'rainbow' livery with small company titles on the forward fuselage.

It was sold to American Finance Group on July 25, 1989 and immediately leased back to United. By June 1991 the aircraft had acquired the larger 'United' titles but retained the existing 'rainbow' livery. On February 01, 1994 the aircraft was withdrawn from use at Oakland, California but was returned to service in May that year.

An indication that its flying days were coming to an end occurred when it was observed at Las Vegas on April 17, 1995 without titles. Repurchased by United Airlines on September 29, 1995 and registered to United Air Lines Inc. it was ferried Las Vegas - Ardmore, Oklahoma on November 01, 1995.

N140UA was sold to Aviation Sales, Ardmore, Oklahoma on December 22, 1995 and cancelled from the United States Aircraft Register on December 26, 1995. Dismantling for spare parts commenced almost immediately. It had been completely scrapped by February 02, 1998 having flown 78,312 hours with 10,700 cycles.