German airline Air Berlin, part-owned by Abu Dhabi's Etihad Airways, has ended its membership of European trade group AEA, citing what it said were its protectionist policies.

The move comes only days after a similar move by British Airways and Iberia, and after the boss of Etihad Airways warned Europe against protectionism in the airline sector.

Air Berlin chief executive Stefan Pichler joined British Airways owner IAG in calling for aviation markets to be liberalised, saying that would promote consolidation and innovation, thereby benefitting all passengers.

"With its current focus and representation of interests, the AEA is not fulfilling these ideas, but allowing itself to be driven by airlines which desperately try to erect a new wall around Europe," Pichler said in a statement on Tuesday.

Etihad, which owns 29 per cent of Air Berlin, has struggled to gain German backing of its code share flights with the German carrier.

Under a bilateral traffic agreement, carriers from the UAE may fly to only four airports in Germany - Frankfurt, Munich, Hamburg and Duesseldorf. Code shares allow it to offer passengers bookings from other airports.

European carriers Air France-KLM and Lufthansa, along with some US competitors, have long complained that the Gulf airlines are benefiting unfairly from interest-free government loans and cheap fuel. The Gulf carriers deny those accusations. - Reuters