Here are the airlines with the most (and least) complaints from passengers last year

A Frontier airlines plane lands at Miami International Airport. The three airlines with the highest ratio of complaints-to-passengers last year were Frontier, Spirit, and JetBlue, according to an analysis by US PIRG Education Fund. It was the second straight year those airlines occupied the top three positions for most complaints.Joe Raedle/Getty Images

Frustrated travelers last year filed the highest number of complaints against domestic airlines in decades, a new report says.

That will come as no surprise to the hundreds of thousands of travelers who got caught in Southwest’s infamous meltdown in December, when the airline canceled more than 16,000 flights around Christmas. Or to anyone who’s been stuck on the tarmac for hours, stranded overnight, or lost their baggage because of a logistical problem.

But the analysis by US PIRG Education Fund, released last month, shows a broad increase in complaints filed with the US Department of Transportation, which regulates the airline industry.

“Air travel is just a mess right now,” said Deirdre Cummings, consumer program director at MASSPIRG Education Fund.

The number of complaints against domestic airlines increased by more than one-third last year, compared to 2021, the analysis shows. And the number of complaints per 100,000 passengers was more than five times higher than before the pandemic.

“Airlines often post unrealistic schedules, they cancel flights, and they drag their feet with refunds,” she said. “Airlines and online ticket agents just don’t face enough consequences when they abuse customers.”

The study looked at a wide range of complaints, including those about cancellations and delays, mishandled baggage, and being involuntarily bumped from flights.

On a complaints-per-100,000-passengers basis, there was a very significant increase in complaints last year among the 17 largest airlines, from 3.1 in 2021 to 5.6, an 80 percent surge, the study says.

The three airlines with the highest ratio of complaints-to-passengers last year were Frontier, Spirit, and JetBlue. It was the second straight year those airlines occupied the top three positions for most complaints.

The three airlines with the lowest number of complaints per passengers last year were Horizon, SkyWest, and Mesa. Among the four biggest airlines — American, Delta, Southwest, and United, which together account for about 80 percent of air travel — Delta had the lowest number of complaints per passenger, the report says.

The largest category of complaints against domestic airlines last year was for cancellations, delays, and misconnections, accounting for about 45 percent of all complaints, the analysis says.

Among the 17 largest airlines, Republic had the highest percentage of its flights canceled, 4.7 percent, while Hawaiian had the lowest, 1 percent, the study says. Among the “big four” airlines, Delta had the fewest cancellations.

Allegiant had the worst on-time record, 63.4 percent, followed by JetBlue (64.6 percent) and Frontier (66.1 percent), the analysis says.

Travelers can get up-to-date information about the on-time performance of airlines by going directly to the Transportation Department’s Bureau of Transportation Statistics.

For flights departing Logan Airport between Jan. 1 and April 30, Southwest had the best on-time performance, 81.6 percent, while Allegiant, American, and United were all about the same at 79 percent, according to the Transportation Department.

The worst on-time performance among the 10 airlines listed on the Transportation Department website were Hawaiian (55.6 percent), Spirit (64 percent), and Frontier (65.1 percent).

In February, the Transportation Department said it was investigating several domestic airlines “to ensure that they are not engaging in unrealistic scheduling of flights,” though it did not name the airlines.

Complaints about not getting refunds made up the second largest category, accounting for about 25 percent of complaints, the US PIRG report says. The airlines most complained about for lack of refunds were American, United, and Frontier.

Among the 17 largest airlines, those that most frequently mishandled baggage, on a per passenger basis, were American, Alaska, and JetBlue, the analysis says. The airlines that least frequently mishandled baggage were Allegiant, Hawaiian, and Frontier.

Another category of complaints was “bumping,” which happens when an airline oversells seats on a flight, usually because it anticipates some ticketed passengers not showing up. Often, airlines offer compensation to ticket-holders who voluntarily give up their seats (and get booked on another flight). But sometimes there aren’t enough volunteers.

In those cases, passengers are involuntarily left behind. Frontier had the worst record on involuntary bumping last year, the study says. Of 10,000 passengers, Frontier involuntarily bumped 2.66, about four times as many as the airline with the next-worst record, Envoy Air.

By contrast, Delta, Allegiant, and Endeavor did not bump a single passenger involuntarily last year, according to the report.

The number of complaints against third-party airfare booking websites for not providing refunds was less than last year, but still much higher than pre-pandemic, the report says.