The A330-300 is the biggest member of Airbus' twinjet family and is closely related to the four engined long range A340 with which it shares near identical systems, airframe, flightdeck and wings, the only major difference being the twin (versus four) engine configuration.

The A340 and A330 were launched simultaneously in June 1987. Although developed in parallel the A330-300 made its first flight after the A340, on November 2 1992. It was the first aircraft to achieve simultaneous European Joint Airworthiness Authorities (JAA) and US FAA certification, on October 21 1993. Entry into service took place by the end of that year.

Differences from the A340 aside from the number of engines are slight changes to the wing and internal systems, including fuel tankage. The A330 (like the A340) takes advantage of a number of technologies first pioneered on the A320, including the common advanced EFIS flightdeck with side stick controllers and flybywire computerised flight control system.

While the standard A330-300 shares the same fuselage length as the A340-300, Airbus has studied various stretched (A330-400) and shortened (A330-100 and 200) versions. The shortened A330-200 was formally launched in 1996 as a long range 767-300ER competitor, and is described separately. One stretched, high capacity concept studied for a time featured lower deck seating in place of the forward freight hold.