Melbourne Airport opened on 1 July 1970, when Prime Minister John Gorton inaugurated international operations at Tullamarine, ending Essendon Airport's nearly two-decade run as Melbourne's international gateway. Domestic flights followed on 26 June 1971, and in its inaugural year the airport handled six international airlines and 155,275 international passengers. The planning that made it possible dated back to 1958, when a government panel set out to find a replacement for Essendon, a site hemmed in by residential development and unable to accommodate the emerging generation of jet aircraft.

Situated roughly 22 kilometres northwest of Melbourne's city centre, the airport operates without a curfew and is Australia's busiest 24-hour airport, handling over 36 million passengers in 2025. That around-the-clock status gives MEL a distinctive character in the Australian network: freight operations fill the early morning hours while passenger banks dominate the daylight schedule. The Melbourne-Sydney route is among the busiest air corridors in the Asia-Pacific region. Qantas, Virgin Australia, and Jetstar all maintain significant bases here, with international carriers including Singapore Airlines, Emirates, Cathay Pacific, and Air New Zealand operating lounges in the international terminal.

The airport's four-terminal layout (one international terminal, 2 standard domestic terminals, and a budget domestic terminal) evolved gradually from the original 3-terminal configuration that opened in 1970. A $330 million expansion of the international terminal was completed in 2011, adding a satellite concourse with floor-to-ceiling runway views. A third runway, approved by the Federal Government in September 2024 and positioned 1.3 kilometres west of the existing north-south runway, is targeted for completion in 2031. One enduring gap: despite proposals stretching back to the airport's opening year, MEL still has no passenger rail link to the city centre.