United Airlines' and Continental Airlines' proposed merger has been approved by European Commission regulators, who have concluded that the tie-up would not damage competition.
The Commission says Continental serves 26 destinations in the European Economic Area and Switzerland while United serves nine.
"As regards air passenger transport, United and Continental's networks are complementary as they have hubs in different US cities," it states.
"The proposed merger therefore only leads to small, incremental increases in the market shares of the parties, where one airline markets seats on flights operated by another carrier or offers an indirect service in competition with a non-stop service operated by the other airline from its US hub."
In the freight sector, the Commission adds, the two airlines' US-European activities overlap but the merger would nevertheless have only a "limited impact" on air cargo transport because of the carriers' "limited presence" in the market.
It states that the inquiry has "confirmed the complementary nature" of the carriers' networks - at least as far as transatlantic services are concerned - and says the tie-up "will not give rise to concerns on any specific route".