EU anti-trust authorities said Tuesday they had opened a full probe into the planned takeover of Greece's Olympic Air by Aegean Airlines.
The European Commission said that the merger of the two main Greek airlines offering passenger air transport services on Greek domestic and international routes raised "concerns that the transaction may lead to price increases and poorer service."
The companies now have until September 3 to respond.
"We have the duty to ensure that Greek passengers and people visiting Greece can travel at competitive air fares," said European Union Competition Commissioner Joaquin Almunia.
Attempts at a negotiated solution failed, the EU executive underlined.