Qatar Airways said on Monday it had started proceedings in a UK court against European planemaker Airbus in a bid to resolve a dispute over surface damage to A350 passenger jets, reports Reuters.
"We have sadly failed in all our attempts to reach a constructive solution with Airbus in relation to the accelerated surface degradation condition adversely impacting the Airbus A350 aircraft," the Gulf airline said in a statement.
Qatar Airways has therefore been left with no alternative but to seek a rapid resolution of this dispute via the courts.
Airbus did not immediately respond to a request for comment.
The two sides have been locked in a row and an underlying layer of lightning protection, which Qatar Airways says has now led to the grounding of 21 jets by its domestic regulator.
The row widened this month when documents seen by Reuters revealed at least five other airlines had complained about paint or other skin flaws since 2016.
Monday's statement was the first formal response after Airbus last week accused one of its largest customers of misrepresenting the problem as a safety issue and threatened to call for an independent legal assessment.
Qatar Airways said it had initiated the legal process in the Technology & Construction division of the High Court in London. Further details of the action were not immediately available.
Airbus has said the A350s have been declared safe to fly by European regulators while acknowledging "surface degradation."
It said last week the airline had refused to apply solutions that it had offered. Qatar Airways said on Monday it could not assess the merits of any proposed repair without a "proper understanding of the root cause of the condition".