The U.K.’s Competition and Markets Authority has launched an investigation into the transatlantic joint venture comprising of American Airlines, British Airways, Iberia and Finnair.

Those airlines are permitted to share revenue and coordinate pricing and scheduling on transatlantic routes.

The agency decided to do the review because the U.K.’s scheduled exit from the European Union means that joint-venture routes between Britain and the U.S. will no longer be subject to European Commission review.

“This case is at an early stage and no assumption should be made that the [joint venture] infringes competition law,” the Competition and Markets Authority said.

In a 2010 review, the European Commission found potential competition concerns on six routes operated by the alliance, including five between London and U.S cities. As a result, the alliance partners made 10-year commitments to make landing rights available at London Gatwick or London Heathrow. The European Commission may reassess that agreement in 2020 but it is not required to do so.

The Competition and Markets Authority estimates that its investigation will be completed next March.