The Royal Australian Air Force (RAAF) has hit a milestone in the development of its new fighter jet fleet with the mid-air refuelling of a United States Air Force F-35A Joint Strike Fighter (bottom left in photo).

The mid-air fuel transfer test in California involved one of the RAAF's KC-30A Multi-Role Tanker Transport planes, according to news.com.au. A total of 59 contacts were made in the four-hour mission, including five hook-ups that transferred about 20,000kg of fuel.

The refuelling operation used the controversial tail-mounted boom system, which had proved to be problematic during the development phase.

The KC-30A jets use either the boom or two "hose and drogue" lines attacked to each wing.

RAAF Air Marshal Leo Davies said mid-air refuelling was critical for the global reach of RAAF aircraft, people and equipment.