"Over the past couple of months, air traffic control capacity issues in Copenhagen have caused considerable problems for airlines, airports and, not the least, our passengers," SAS CEO Anko van der Werff said in a statement.

"We will seek compensation for the irregularity costs caused by the situation," he said without elaborating.

Naviair, the company controlling air traffic in Danish airspace, shed 46 air traffic controllers in voluntary layoffs during the COVID-19 pandemic, leaving remaining staff to take additional paid shifts as travel later recovered.

But Naviair controllers in late April began turning down the extra work in a conflict over work hours, leading to delays and cancellations.

Norwegian Air, a rival to SAS, last month also voiced concerns over the situation in Copenhagen, adding that this could disrupt busy summer traffic.

(Reporting by Terje Solsvik, editing by Anna Ringstrom)