Alaska Airlines slipped past rival Hawaiian Airlines to post the best on-time rating for U.S. carriers in July.
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A total of 21 planes were stuck on the ground longer than federal rules allow, which is three hours for domestic flights. That's the highest number of long delays in more than a year, and it could mean fines for the airlines involved.
The Department of Transportation said Tuesday that 75.2 percent of flights on the main airlines were on-time. That's down from 78 percent in June and 78.1 percent the previous July.
The biggest four airlines finished in the middle of the pack, with Delta best in the group followed by United, Southwest and American.
Nearly 2 percent of all flights were canceled, including 2,300 on Southwest after a computer outage.