The 40-year concessions to upgrade and operate the airports, including in Greece's second largest city Thessaloniki, were awarded in 2014 to a consortium of Fraport and Cyprus's Copelouzos Group for 1.234 billion euros (1.07 billion pounds).

The Commission said it had found that the concession agreements were in line with market conditions, with Greece selecting the best offer submitted in a tender.

The concession awards were part of a privatisation plan to which Greece committed in return for funds from lenders.

($1 = 0.9282 euros)

(Reporting By Philip Blenkinsop; editing by Robert-Jan Bartunek)