More flights delayed in August, government reports

— -- More than one of every five flights in the U.S. was delayed in August and customer complaints against the airlines rose sharply, new data from the federal government out Thursday shows.

The 16 largest U.S. airlines recorded just 79.3% of their flights got to their destinations on time in August. That's down from 81.7% a year ago, but up from 77.8% in July, according to the Transportation Department's Bureau of Transportation Statistics.

About 40% of the delays were caused by factors resulting from bad weather, including aviation system delays and the snowball effect of late-arriving aircraft for connecting flights, the bureau says. A flight is considered on time if it arrives within 15 minutes of schedule.

At the same time, the number of complaints the Transportation Department received from customers about bad airline service rose 18.1% from a year ago to 1,471 complaints. It increased 10.3% from the total of 1,285 filed in July.

Cancellation rates also shot up, with the carriers grounding 2.5% of their scheduled domestic flights in August — or 13,726 out of 541,442 flights. That compares to 1% year ago and 1.7% in July.

There were three planes stuck on airport tarmacs more than three hours in August, compared to one in August 2010 and one in July 2011. Delta reported two of the three lengthy tarmac delays, both on August 19 at New York JFK.

Other findings:

•Hawaiian Airlines reported the highest on-time arrival rate at 94.8%, followed by Alaska Airlines and Southwest Airlines. The worst performing carriers were JetBlue (61.6% on-time rate), US Airways (74.2%) and Continental (74.3%).

•The U.S. carriers reported a mishandled baggage rate of 3.44 reports per 1,000 passengers in August. That's up from August 2010's rate of 3.42, but down from July's 3.71.