Prior to the start of the project, de Havilland had determined that a successful business jet would require several variables to be met, including a range of at least 1,000 miles (1,600 km), the speed and cost factors of a suitable jet engine to outperform turboprop-propelled competitors, and an engineering philosophy that favoured reliability and conventionality.

Hawker Siddeley had bought de Havilland the year before the project had started, but the legacy brand and "DH" designation was used throughout development.

Writing in 1993, Flying Magazine said of the type "In numerical terms, the 125 series is the most successful British commercial aircraft ever built, and the world's longest in-production business jet".

[2] Production of the aircraft came to an abrupt halt in 2013 due to the bankruptcy of owner Hawker Beechcraft, who has suffered during the Great Recession of the late 2000s in which demand for business jets had slumped for a number of years.

[14] The aircraft is equipped with a de-icing system, which uses a mixture of bleed air from the engines, TKS fluid for general airframe, and AC electric windshield heating to prevent ice formation.

[5] The rear of the fuselage has a large equipment bay and, on some aircraft, one or two additional fuel tanks for extended operations.

[8] The Royal Air Force was a significant early operator of the type, receiving 20 aircraft equipped as a navigation trainer and designated Hawker Siddeley Dominie T.1.

[20] By the early 1990s, British Aerospace, the manufacturer of the type at this point, had two main variants of the aircraft in production; the smaller 125-800 and larger 125–1000.

The 125–1000, which conducted its first flight on 16 June 1990, had several changes to give the type a reported intercontinental range, including the adoption of the newly developed Pratt & Whitney Canada PW300 engine and new digital avionics, such as FADEC.

[9] The 125 is the only business jet to have been hijacked: in 1967, a chartered 125 carrying the former Congolese Prime Minister Moise Tshombe was diverted to Algeria by armed persons on board.

[23][24] While badly damaged by the direct hit (which resulted in the loss of an engine, decompression of the cabin, and rupture of its fuel tanks) the aircraft was successfully landed by BAe demonstrator pilot Arthur Ricketts.

[2] In 2013, the FAA modified its rules to prohibit the operation of jets weighing 75,000 pounds (34,000 kg) or less that are not stage 3 noise compliant, specifically mentioning the 125 series of aircraft.

This required any aircraft of the type either to have compliant engines installed, or to be fitted with a hush kit, to fly over most of the United States after 31 December 2015.

Data from Jane's All The World's Aircraft 1976–77,[75]General characteristics PerformanceMaximum Operating Mach number (MMO