DUBAI, United Arab Emirates — Qatar Airways said Thursday that it grounded 13 Airbus A350s over what it described as fuselages “degrading at an accelerated rate” in the long-range aircraft, further escalating a monthslong dispute with the European airplane maker over the issue.

While Airbus declined to specifically discuss the announcement, Qatar Airways’ decision to ground the aircraft raised questions about the A350s’ carbon composite fuselage, designed to make the twin-aisle aircraft lighter and cheaper to operate by burning less jet fuel.

Qatar Airways also is one of the world’s top operators of the aircraft.

In its statement, Qatar Airways said it had been monitoring the degradation beneath the paint on the fuselage of the aircraft for some time. It described the issue as a “significant condition,” without elaborating.

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

In June, Qatar Airways said it wouldn’t take any more A350s unless the problem was fixed.

Airbus declined to specifically discuss Qatar Airways’ grounding.

Singapore Airlines is now the world’s top operator of the A350, with 56 in its fleet. The airline did not respond to a request for comment. In the U.S., Delta Air Lines has 15 in its fleet. The Atlanta-based carrier did not respond to a request for comment.

The A350 has a list price as much as $366.5 million, though buyers often get discounts in bulk deals.