American Airlines and its four “Oneworld” alliance partners - British Airways, Iberia Airlines, Finnair and Royal Jordanian Airlines – have received tentative approval from the US Department of Transportation (DOT) to expand their transatlantic alliance in return for renouncing four daily pairs of Heathrow slots at crammed Heathrow airport in London.

With the US regulators likely to grant antitrust immunity to the “Oneworld” alliance partners, the airlines – who will be able to coordinate international operations more closely in transatlantic markets - must accept the conditions pertaining to the protection of consumers as well as the preservation of competition.

This is the third time since 1998 that American Airlines and British Airways have sought immunity for extending their alliance. While these two airlines welcomed the Saturday decision by the DOT, fellow partner Iberia Airlines had insisted that the enhanced alliance should not have any conditions imposed on it.

The DOT’s approval, which is conditional on a comment period lasting 90 days, will bring “Oneworld” at par with SkyTeam and the rival Star alliance, in terms of flexibility of coordinating fares, schedules and marketing on transatlantic routes.

While the DOT noted that the alliance might adversely affect competition on select routes between the US and Heathrow Airport, the alliance partners said they would “review the DOT’s tentative order and will respond according to the timeframe established for comments.”