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Airlines are reporting better unit revenues for the tail end of summer, a sign customers will continue to have to shell out more to fly in the coming months.

Delta Air Lines said domestic and trans-Atlantic unit revenue would be up in September from last year, though it said the CrowdStrike outage in July will mean unit sales will rise no more than 1% compared with a previous forecast of as much as 4% higher for the quarter. Delta has said it expected a $500 million hit from the outage and its aftermath, when it canceled some 7,000 flights.

Alaska said it had a tail wind from the outage, which affected Delta customers more than those on other airlines.

"While capacity remains in line with prior expectations, revenue has performed better than anticipated driven by additional revenue in July related to CrowdStrike disruptions across the industry and stronger performance in August and September," Alaska said in a securities filing.

Delta's president, Glen Hauenstein, told a Morgan Stanley conference on Thursday that Delta isn't seeing a lingering impact on bookings from the outage.

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