A spat between Airbus and Qatar Airways has led to the European plane maker to terminate a multi-billion-dollar order with the Middle Eastern airline for 50 of its single-aisle in-demand A321neo jets.

The termination of the contract for the A321neos comes as Airbus and the airline – one of its biggest customers – escalate a legal dispute over the grounding of the larger twin-aisle A350 plane.

In December, Qatar’s national carrier announced it was suing Airbus in London over what it described as the “accelerated surface degradation” of the wide-body A350. Qatar Airways said it had no choice but to ground a number of the jets, with 21 now out of operation.

The termination of the Airbus contract for its 321neos follows on the heels of Qatar Airways refusing to take any more A350s until the problem is fixed.

The state-owned airline will be relying on the long-haul A350 for the increased inflow of passengers to Qatar for the month-long FIFA 2022 World Cup, which will be played in the Arab Gulf state starting Nov. 21.

Qatar Airways has a fleet of 53 Airbus A350s in both its 1000 and 900 series. The airline has more on order with the France-based airplane manufacturer, making its total order of 76 A350s the most of any airline worldwide.

In a brief comment to the Associated Press, Airbus confirmed that it did terminate a contract for 50 A321s ordered by Qatar Airways. The airline did not provide further details.

In a public statement last year, Qatar Airways said it was left with no alternative but to seek a resolution through the courts to ensure that Airbus undertakes a thorough investigation of the full root cause of the degradation beneath the paint on the fuselage of the aircraft. Qatar Airways says otherwise it is not possible to establish whether any proposed repair solution will rectify the underlying condition.

Airbus had said it intends to vigorously defend its position as no other airline flying the A350 has grounded the aircraft due to safety concerns.