Aircraft designers have always pushed the envelope to develop supersonic transport (SST) aircraft.

The main advantage of SSTs is its supersonic speed which significantly reduces the trip time between two cities. Its main drawback is the sonic boom created by the supersonic speeds.

To date, only two SSTs, the Tupolev Tu-144 and Anglo-French Concorde have entered commercial operation.

The Tupolev Tu-144 is a Soviet supersonic passenger airliner designed by Tupolev that was in operation from 1968 to 1999.

The Tu-144 was the world's first commercial supersonic transport aircraft. The prototype's maiden flight was on December 31, 1968, from Zhukovsky Airport in Moscow. The aircraft was a product of the Tupolev Design Bureau, headed by aeronautics pioneer Aleksey Tupolev. Sixteen Tu-144 aircraft were manufactured.

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The Tu-144's first supersonic flight was on June 5, 1969 and on May 26, 1970 it became the world's first commercial transport to exceed Mach 2.

The Tu-144 conducted 102 commercial flights at an average service altitude of 52,000 ft and a cruising speed of around 1,522 mph.

Reliability and developmental issues restricted the viability of the Tu-144 for regular commercial use.

These factors, together with repercussions of the Tu-144 crash at the 1973 Paris Air Show, projections of high operating costs, and rising fuel prices and environmental concerns outside the Soviet Union, caused foreign customer interest to wane.

The Tu-144 was introduced into commercial service with Aeroflot between Moscow and Alma-Ata, Kazakhstan on November 1, 1977.

It was withdrawn less than seven months later after a new Tu-144 variant crash-landed during a test flight on May 23, 1978.

The Tu-144 remained in commercial service as a cargo aircraft until the cancellation of the programme in 1983.

It was later used by the Soviet space programme to train pilots of the Buran spacecraft and by NASA for supersonic research until 1999.

The Tu-144 made its final flight on June 26, 1999 and surviving aircraft were put on display across the world or into storage.

The Concorde is an Anglo-French supersonic airliner jointly developed and manufactured by Sud Aviation (later Aerospatiale) and the British Aircraft Corporation (BAC). Studies started in 1954 and on November 29, 1962, France and the UK signed a treaty establishing the development of the project.

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The programme cost was estimated at £70 million at that time. Construction of the six prototypes began in February 1965, and the first flight took off from Toulouse on March 2, 1969. The market forecast was for 350 aircraft and up to 100 option orders were placed by many major airlines.

It received its Certificate of Airworthiness from France on October 9, 1975 and from the UK on December 5, 1975.

Delays and cost overruns increased the programme cost to £2.1 billion in 1976.

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