WICHITA, Ks. — According to the 26th annual national Airline Quality Report, Virgin America has been rated the top airline for the fourth year in a row when it comes to quality among the biggest U.S. carriers.
The report was released Monday, the same day Alaska Airlines announced that it will buy Virgin America for $2.6 billion.
The airline's overall score declined slightly from 2014, but Virgin America still managed to retain its top ranking for 2015. JetBlue finished second, followed by Delta Air Lines.
Despite overall industry improvement in three of the four categories tracked, customer complaints rose by 38% from 2014 to 2015, according to the report.
"This is the worst complaints have been for 15 years, as a rate. The last time it got this high was in 2001," said report co-author Dean Headley, a researcher at Wichita State University's business school.
The report uses performance data gathered from the U.S. Department of Transportation's monthly Air Travel Consumer Report to see whether public impressions of airline quality actually line up with airline performance.
The rating report looks at four performance categories: on-time performance, mishandled bags, involuntary denied boardings and customer complaints.
According to the report, overall airline performance improved slightly in 2015. The industry showed overall improvement from 2014 to 2015 in on-time performance, mishandled bags and involuntary denied boardings.
Six of the 13 airlines evaluated -- JetBlue, Delta, ExpressJet, SkyWest, Southwest and United -- improved their overall scores.
Six others, including Virgin America, declined from 2014, and Spirit Airlines was new to the ratings.
American Airlines, which has a hub in Charlotte, dropped from 7th to 10th.
CLICK HERE to read the full report.
Overall airline ranking, with 2014 rankings in parentheses
1. Virgin America (1)
2. JetBlue (4)
3. Delta (3)
4. Hawaiian (2)
5. Alaska (5)
6. Southwest (6)
7. SkyWest (10)
8. United (9)
9. ExpressJet (11)
10. American (7)
11. Frontier (8)
12. Envoy Air (12)
13. Spirit (new to rating in 2015)
CNN contributed to this article.