Italy's anti-trust authority has launched a probe into Alitalia's acquisition of smaller Italian airline Volare to see if conditions it imposed when the merger was authorised were effective.

The watchdog said a new industrial plan by Alitalia -- which includes major changes in its use of airports in Milan and Rome -- meant it needed to reassess the conditions it imposed when allowing the merger last year.

The authority had ordered Alitalia to give up take-off and landing slots on several domestic routes.

Alitalia is in search of a buyer for the 49.9 percent stake that the Italian state has said it wants to sell, fully privatising the flag carrier.