EU competition regulators are investigating whether pricing and capacity pacts between Air France-KLM, Alitalia and Delta on transatlantic routes are bad for passengers.
The European Commission said: “The goal is to ensure that this tie-up does not harm passengers on EU-US routes.”
It said it would consider the implications of the joint venture compared to the situation where the airlines would otherwise be competing.
The agreements signed between the airlines in 2009 and 2010 cover coordinated transatlantic operations in terms of capacity, schedules, pricing and revenues.
“The parties also share profits and losses of their transatlantic flights,” said the Commission, which acts as competition regulator for the European Union.
Alliances allow their members to streamline costs, share revenues and increase scale, a better option for airlines than mergers, which can be difficult and expensive to achieve.
At the same time Brussels said it had closed separate formal competition proceedings against several members of the SkyTeam alliance: AeroMexico, Air France and KLM, Alitalia, Czech Airlines, Delta, Korean Air Lines and Continental.