Airlines are doing a better job of staying on schedule now that fewer people are flying.

The U.S. Department of Transportation said Wednesday that 83.8 percent of domestic flights arrived on time in September, slightly better than September 2012’s 83.3 percent rate. It was a bigger improvement over July and August, when summer vacationers packed the nation’s airports and about 1 in 4 flights arrived late.

Hawaiian Airlines held its usual top spot in the ratings, with 95.5 percent of flights arriving within 14 minutes of schedule. Of the 16 reporting carriers, Southwest Airlines ranked last, with a 76.3 percent on-time mark.

Southwest spokeswoman Brandy King said "unexpected summer weather" and schedule changes caused delays.

"We are aware of the pain points and are working on schedule tweaks that will improve our performance in the next few months," she said.

Just under 1 percent of flights were canceled in September, up slightly from a year earlier.

Hawaiian also scored high for fewest flight cancellations at 0.1 percent, representing four cancellations out of 5,831 total flights. In other categories, Hawaiian was third for passengers bumped from their flights with 0.08 people per 10,000 passengers; and eighth for both fewest mishandled baggage reports with 2.43 reports per 1,000 passengers, and consumer complaints with 0.77 per 100,000 passengers.

The Transportation Department said three September flights might have violated federal rules on tarmac delays. Two were operated by United Airlines and one by Spirit Airlines. The Transportation Department said it was investigating the incidents.

Last month, the agency fined United $1.1 million for stranding passengers on 13 planes during a lengthy weather delay in Chicago in July 2012 — the biggest fine ever for overly long tarmac delays.

Travelers are lodging fewer complaints about the airlines.

Through the first nine months of the year, complaints filed with the Transportation Department are running 14 percent lower than during the same period in 2012.

Through September, the rate of bags being lost, damaged or delayed was slightly higher than in 2012. Virgin America rated best at bag handling; American Eagle was last.

From July through September, airlines bumped 11,721 people, down 24 percent from the same period last year.

About 109,000 passengers voluntarily gave up seats as airlines frequently offer travel vouchers to encourage volunteers to leave oversold planes.

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Star-Advertiser reporter Dave Segal contributed to this story.