Complaints about airline service continued to soar in June, as airline passengers registered more than five times as many gripes about delayed flights, lost bags and other problems as they did a year ago.

Continental Airlines continued to lead the list of airlines that made passengers mad enough to write or call the Department of Transportation.

Second in the rankings was Eastern Airlines, which like Continental is owned by Texas Air Corp.

Together the two airlines accounted for approximately 45 percent of all complaints filed against U.S. airlines.

According to the DOT, 1,507 passengers complained about Continental's service -- or 41.93 for every 100,000 passengers carried.

DOT said that 809 passengers -- or 19.6 per 100,000 -- complained about Eastern's service.

Northwest Airlines, Trans World Airlines and Pan American World Airways were next in the ranking, measured by how many complaints were filed per 100,000 passengers.

Delta Air Lines had the lowest rate of complaints filed against any major U.S. carrier.

"Everybody's are up," said Paula Musto, a spokeswoman for Eastern Airlines. Musto said that she thought recent attention to problems in the airline industry contributed to the increase in complaints.

She also said that some of the complaints were prompted by innovations in the industry that consumer do not yet understand. "A lot of people still don't understand the concept of nonrefundable tickets," she said.

The total number of complaints about U.S. airlines during June was 5,155, up from 843 a year ago and double last month's 2,577.

As usual, complaints about flight problems, including delays, led the list.

Continental noted that the increase in the number of complaints for the industry as a whole from May to June was greater in magnitude than the rise in complaints about Continental. A Continental spokesman said that the airline's own internal measurements have shown service improving since the first of the year.

The deteriorating quality of airline service has prompted both Congress and DOT to intervene.

On Tuesday, the Senate Commerce Committee approved a bill that would require airlines to report how frequently flights are late or canceled, how many bags are lost and how many consumers are bumped from flights because of overbooking.

The House Energy and Commerce Committee, on the same day, approved an amendment to a bill providing funding for the Federal Trade Commission, giving the FTC jurisdiction over fraudulent and deceptive practices by airlines.

In May, Transportation Secretary Elizabeth Hanford Dole warned the airlines of possible federal action unless service improved, and on Monday 13 airlines agreed to voluntarily provide data to DOT about on-time performance, lost baggage and other problems.