Douglas DC-4s equipped the airline during World War Two and were used for domestic services early in 1946. The type was subsequently replaced by DC-6s.

Caravelle Jet Mainliner became the promotional name for the 20 French-designed airliners purchased from Sud-Aviation.

United ordered seven Boeing 377 Stratocruisers and used them principally on the Hawaii route. Six were subsequently sold to BOAC.

A stylised ‘U’ identifies all United Airlines aircraft, this view showing the tails of a Boeing 757 (foreground), 727 and 737 parked on the ramp at Chicago O’Hare.

The Boeing 727 was UAL’s mainstay on the short and medium-haul routes and by the mid-1980s more than 150 were in service. Some 20 years separate the two examples pictured and serve to highlight the change in livery.

The Boeing 727 was UAL’s mainstay on the short and medium-haul routes and by the mid-1980s more than 150 were in service. Some 20 years separate the two examples pictured and serve to highlight the change in livery, the latest scheme being shown here.

April 1992 and Boeing pose four different aircraft awaiting delivery to UAL. Clockwise from the left: 737-500, 747-400, 767-300ER and a 757-200.

Another British type in United Express service is the Jetstream Super 31, N487UE being pictured taxiing out at JF Kennedy in front of a Boeing 747-400.

Air Wisconsin/United Express BAe ATPs with a BAe 146 during a ‘bank’ at O'Hare in August last year.

Following the purchase of Capital Airlines, Vickers Viscounts' donned UAL colours and became an important type with the airline.

Douglas DC 7 N6322C ‘Mainliner Waipahu’ of UAL over Hawaii. This was one of 57 of the type purchased hy United and was essentially a direct development of the DC-6B.

Revolutionary when it appeared, the Boeing 247 was ordered by UAL, 59 of the first 60 being completed for the airline. This preserved example carries the early grey colour used by all UAL aircraft until 1940 when the scheme was changed to blue and white.

Salvaged from a dump in Alaska in 1964, this Boeing 80A was rebuilt to display standard and is now on display at the Museum of Flight in Seattle, Washington. It carries the colours of Boeing Air Transport Inc which became part of the United Aircraft & Transport Co.

United began taking delivery of the new, smaller Boeing 737-500 in 1991-92 and N922UA is one of the batch and is seen at Chicago O’Hare.

A replica of the Wright J-4-powered Swallow biplane, five of which were operated by Varney Air Lines on US Mail contracts in the late-1920s. It is generally accepted that this was the first aircraft operated by the company that was to emerge as United Airlines.