WASHINGTON -- More flights are arriving on time but consumer complaints about the airlines have risen sharply.
The U.S. Department of Transportation reported Thursday that the nation's leading carriers posted an on-time rate of 80.3 percent in August. That was better than the 78.1 percent mark in July and 77.7 percent the previous August.
Delta Air Lines had the best on-time rate, 85.5 percent, followed by Alaska Airlines at 82.9 percent.
Spirit Airlines rated last, with an on-time rate of 63.7 percent. JetBlue Airways was next to last at 74 percent.
The government counts a flight as on time if it arrives within 14 minutes of schedule.
Two domestic flights in August were stuck on the tarmac longer than three hours, which could trigger violations of federal rules. One was a Delta flight delayed at Orlando, Florida, and the other was a PSA Airlines flight held up at Charlotte, North Carolina. PSA operates US Airways Express flights.
Consumers filed 1,633 complaints about U.S. airlines with the government, up from 1,107 a year earlier.
Complaints most frequently concern delayed flights, but baggage or ticketing problems, customer service and fares are also included.
Spirit had the highest complaint rate by a wide margin. Consumers were nearly twice as likely to complain about Spirit as about Frontier Airlines, the carrier with the second-worst record. Both airlines advertise low fares but charge more fees than most other carriers.
Many more travelers complain directly to the airlines, so the government report does not fully capture consumer displeasure.
The CEO of Frontier Airlines estimated that his company gets 30 complaints for every one filed with the government.