Sunwing Airlines said on Tuesday that thousands of passengers remained stranded, and the start of vacations delayed for others, as the company continued to struggle with a technical problem that has grounded flights.

The airline said about 15 out of the more than 40 scheduled flights had been processed since the technical issue first surfaced, but that its check-in systems provider continued to experience a system outage.

Sunwing said Airline Choice was working with relevant authorities to find a solution as soon as possible and was processing flights manually, subject to airport restrictions, curfews and required crew reassignments.

Some of the planes were waiting to return to Canada, which delayed the start of vacations for other travellers.

Sunwing apologized to passengers “whose travel plans have been impacted” and urged them to sign up for flight alerts on its website at Sunwing.ca.

“Our team has been working day and night to find alternate ways to get customers to their destination or on return flights home,” it said in a news release.

The tour operator has said the problem also affected other airlines, snarling their traffic as well.