The European Commission said it had concerns that the two airlines pursued an anti-competitive strategy on the Brussels-Lisbon route by discussing a capacity reduction, granting each other unlimited rights to sell seats on each other's flights and aligning their ticket prices.

"We are concerned that in this particular case Brussels Airlines and TAP Portugal may have used their codeshare to restrict competition and harm passengers' interests on the Brussels to Lisbon route," said Margrethe Vestager, the EU's competition commissioner.

(Reporting by Julia Fioretti and Philip Blenkinsop; Editing by Alissa de Carbonnel)