U.S. airlines' on-time performance improved in August, the Department of Transportation said Tuesday, although it mishandled more bags and received more complaints than a month earlier.

The DOT's Bureau of Transportation Statistics said the 19 carriers reporting on-time performance had an overall rate of 79.7%, up from 78.4% a year earlier and 77.6% in July. The agency said carriers canceled 1% of their scheduled flights, compared with 1.6% a year earlier and 1.2% in July.

A flight is counted as "on time" if it operated less than 15 minutes after the scheduled time shown in the carriers' computerized reservation system.

Regional carrier Comair Ltd. (COM.JO) again had the worst on-time performance in August at 65.9%, while Hawaiian Holdings Inc.'s (HA) Hawaiian Airlines again had the best, with a 94.7% rate. Atlantic Southeast Airlines had the second-worst rate, at 69.5%, followed by AirTran Holdings Inc.'s (AAI) carrier and Northwest Airlines at 74.2% and 74.4% respectively. Alaska Air Group Inc.'s (ALK) airline followed Hawaiian atop the timeliness list at 85.8%.

The most frequently delayed trip for August was Pinnacle Airlines flight 896 from Knoxville, Tenn., to Atlanta, which was late 94% of the time. Pinnacle is the only airline that voluntarily reports data to the department.

Meanwhile, the industry had a mishandled baggage rate of 4.04 per 1,000 passengers in August, down from 4.98 a year earlier but worse than July's 3.98 rate. The DOT also received 888 complaints in August, compared with 1,006 and 827, respectively.

-By Joan E. Solsman, Dow Jones Newswires; 212-416-2291; joan.solsman@dowjones.com