DALLAS — At the height of this summer’s travel season, airline flights were more likely to arrive on time and less likely to be canceled than they were last year.

The airlines’ improved performance in July was a welcome break for travelers. Over the first six months of 2014, delays were the highest since 2008 and cancellations the highest since 2000. The U.S. Department of Transportation said Wednesday that among 14 of the largest airlines, 75.6 percent of flights arrived on time in July, up from 73.1 percent in July 2013 and from June 2014’s 71.8 percent rate.

The airlines covered by the report canceled 1.6 percent of their trips, down from 1.7 percent a year earlier and 2 percent in June.

The best for arriving on time were Hawaiian, Delta and Alaska, all above 84 percent.

At the bottom of the rankings: JetBlue Airways and Southwest Airlines, with nearly one in three flights arriving late.

JetBlue spokesman Morgan Johnston said the airline was making better use of spare planes and adjusting staffing in its operations center to handle delays during summer thunderstorms. He said the airline’s August numbers, not yet released by the government, were better.

Southwest had a pattern of consistently late arrivals on many routes. According to the government, Southwest ran late more than half the time in May, June and July on three short daily flights — a 6 p.m. Houston-Dallas trip, a 7:45 p.m. flight from Los Angeles to San Francisco, and a 9 p.m. Las Vegas-Phoenix flight. No other airline had any flights that were tardy so often for so long.

Another 108 Southwest flights regularly ran late for two straight months. No other airline had more than six such chronically delayed flights.