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 one in four flights arrived late.
Hawaiian Airlines held its usual top spot in the ratings, with 95 percent of flights arriving within 14 minutes of schedule. Of the 16 reporting carriers, Southwest Airlines ranked last, with a 76 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.
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.