Virgin Australia and Delta Air Lines have gained final regulatory clearance for their alliance on routes between Australia and the US. The final approval from the ACCC on Friday for Virgin’s other alliance with Delta for a further five years falls short of the 10 years that the airlines were seeking.

The regulator said it had given approval for a shorter period because of the “ongoing evolution of services on the trans-Pacific and the dynamic nature of the aviation industry”. Virgin flies daily to Los Angeles from both Sydney and Brisbane, while Delta has a daily flight between Sydney and LA. Between them, the two airlines have a 37 per cent share of traffic on the key Sydney-LA route.

The alliance with Delta is one of four key alliances Virgin has cemented since 2009. But unlike those with Air New Zealand, Etihad and Singapore Airlines, Delta does not have a stake in Australia’s second-largest airline.

Competition between Australia and the US is set to intensify in December when American Airlines, which has not flown to Australia since the 1990s, begins daily B777-300ER services between Sydney and LA.

The expansion is part of an intensifying of its alliance on the transpacific route with Qantas, which will result in the Australian airline redeploying its B747-400s fly between Sydney and San Francisco, ending the monopoly that United Airlines has held on the route.

Their expansion will boost capacity between Australia and the US by nine per cent. Last month, the ACCC gave Qantas and American Airlines interim approval despite opposition from Air New Zealand and Hawaiian Airlines.