Airlines recorded their best on-time performance for the first four months of the year in 18 years on record, according to the latest federal data.

Overall, airlines posted an on-time arrival rate of 84.5 percent for the period from January through April of this year, benefiting from a relatively mild winter.

Delta Air Lines ranked third for on-time performance over that period with 88.2 percent of flights arriving on time, while AirTran Airways ranked second with a 91 percent on-time rate, trailing only Hawaiian Airlines.

Delta said its improvements come from an increase in maintenance stations and a focus on on-time departures, training, and recovery from delays and cancellations. "Focusing on those items ... we're getting better at hitting them," Delta spokesman Anthony Black said.

Delta and AirTran are the two largest carriers at Hartsfield-Jackson International Airport.

Airlines also posted their lowest flight cancellation rate in 18 years for the year through April, with 1.1 percent of flights canceled.

Hartsfield-Jackson ranked 11th among major airports in on-time arrival performance for the year through April, up from 18th in the same period of 2011.

For the month of April, airlines posted their fifth-best on-time arrival performance for any month on record, with 86.3 percent of flights arriving on time, up from 75.5 percent a year earlier.

Still, the number of complaints about airlines to the federal government increased, to 1,068 in April from 880 in April 2011. That included 94 complaints about delays, up from 87 a year earlier. Complaints to the U.S. Department of Transportation also increased in other areas, including customer service, baggage, refunds, fares, and reservations, ticketing and boarding.