BRUSSELS -  British Airways and Iberia owner International Airlines Group's ICAG.L has offered concessions to address EU antitrust concerns over its 500-million-euro ($579.6 million) bid for Spain's Air Europa, a European Commission filing showed on Thursday.

IAG put in its offer on Wednesday. The EU executive, which did not provide details in line with its policy, extended its deadline for a decision on the deal to Jan. 4.

IAG signed a deal with Spanish airline Volotea in March last year to buy several of IAG's routes to bolster competition on the domestic market in an attempt to allay regulatory concerns but did not detail which routes.

The EU antitrust watchdog is now expected to seek feedback from rivals and customers before deciding whether to accept IAG's offer or demand more concessions in return for the green light.

It had previously said the deal would reduce competition on Spanish domestic and international routes.

($1 = 0.8627 euros)

(Reporting by Foo Yun Chee; editing by Jason Neely)