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DALLAS (AP) – Delta Air Lines says some computer systems are still working slowly more than a day after an outage crippled the airline and led to more than 1,500 cancelled flights.

Chief Operating Officer Gil West says that the airline is seeing slowness in a system used to check in and board passengers and dispatch planes.

West is giving the airline’s most detailed description yet of what happened Monday to trigger a global outage of its computer systems.

He says a piece of power equipment failed, causing a loss of power. Key systems and equipment then did not switch over to backups.

Delta canceled more than 1,000 flights Monday and more than 500 by Tuesday afternoon.

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