The controversial transatlantic tie-up between American Airlines, British Airways and Iberia has won final approval from the US Department of Transport, some 14 years after it was first proposed.

The green light clears the ways for the three carriers to jointly set prices, sell tickets and schedule flights through their Oneworld alliance, exempt from antitrust rules, the DoT said in a statement.

The decision follows last week’s approval by the European Union, and comes after two previous refusals by the regulators.

Separately, the DoT has also granted antitrust immunity to fellow oneworld members Finnair and Royal Jordanian.

Willie Walsh, chief executive of BA, described the transatlantic decision as “fantastic news”.

He said: “This is a great day for all three airlines and the oneworld alliance. We’ve waited 14 years to bring the benefits of the trans-Atlantic joint business to our customers and level the playing field with the other two global alliances.”

“As we have argued all along, the EU-U.S. market is highly competitive and Heathrow’s liberalization in 2008 opened it up even further. We are delighted that the U.S. and EU authorities have recognized this.”

However Virgin Atlantic’s Sir Richard Branson branded the DoT’s decision a “monster monopoly,” saying that the US regulator “has decided to put the interests of BA and AA before those of the flying public.”

The alliance is viewed within BA as being more important to its future than its pending merger with Spain’s Iberia, with chairman Martin Broughton last year saying that it is worth “hundreds of millions” of pounds to the British flag carrier.

The airlines are expected to launch a joint trans-Atlantic business this Autumn, co-operating on flights between the EU and the US, Canada and Mexico.

As part of the DoT’s approval, however, the airlines will be forced to give up four pairs of slots at London’s Heathrow airport to allow greater competition.

The decision by the DoT follows a similar decision from the European Commission a week ago.