The number of complaints filed by air travelers with the U.S. Department of Transportation jumped 30 percent in 2015 over the previous year, with complaints about airfares nearly doubling, according to data released Thursday by the federal agency.

Spirit had the highest complaint rate, more than twice as high as its nearest rival, Frontier Airlines. Hawaiian had the lowest complaint rate.

Air travelers filed 20,170 complaints in 2015, compared with 15,539 complaints in 2014, with the greatest number of complaints filed against American Airlines, the nation's largest carrier. Complaints over fares nearly doubled to 1,813 in 2015 from 916 in 2014.

In addition, Spirit also had the worst on-time performance.

Overall, U.S. airlines are doing a slightly better job of keeping flights on schedule although more than one in five flights still arrives late.

DOT said Thursday that 77.8 percent of domestic flights in December arrived within 15 minutes of schedule - that's on-time, according to the government.

That's up from 75.3 percent the previous December, although it's down from November's 83.7 percent on-time rate.

Hawaiian Airlines had the best on-time performance.

Passengers on 14 December flights were stuck on the ground longer than allowed by federal rules.

Here are the government's rankings of the leading airlines and their on-time performance for December. The federal government counts a flight as on time if it arrives within 14 minutes of schedule.

1. Hawaiian Airlines, 93.0 percent

2. Alaska Airlines, 85.3 percent

3. Delta Air Lines, 83.6 percent

4. Envoy Air, 80.4 percent

5. American Airlines, 79.2 percent

6. United Airlines, 77.9 percent

7. ExpressJet, 77.3 percent

8. Southwest Airlines, 76.1 percent

9. Frontier Airlines, 75.0 percent

10. SkyWest Airlines, 72.9 percent

11. Virgin America, 71.1 percent

12. JetBlue Airways, 70.1 percent

13. Spirit Airlines, 68.7 percent

Total, 77.8 percent

The Associated Press contributed to this report.