Airline delays and cancellations could reach near-record levels this summer at major airports such as Washington Dulles International and other hubs, the Department of Transportation inspector general told lawmakers yesterday.

Spurred by low-fare airlines and the growth of small jet planes, some airports this summer are expected to be as busy as the summer of 2000 -- an infamously frustrating year for air travel in which nearly one of every four flights was delayed or canceled, Inspector General Kenneth M. Mead said in written testimony. Already, airline delays are up 24 percent in the first quarter of 2004 compared with the same period a year ago.

Dulles is expected to be particularly clogged because new low-fare carrier Independence Air is expected to add 300 daily flights, contributing to a 17 percent increase in traffic this summer from last summer, Mead said. Airports in Philadelphia, Atlanta, San Antonio, Cincinnati and Fort Lauderdale, Fla., along with La Guardia in New York and O'Hare in Chicago, are expected to surpass 2000 passenger levels.

"The potential for congestion and delays this summer in some key airports is very real and the highest it has been since that terrible summer in 2000," Mead said.

He urged the Federal Aviation Administration to complete its review of airports that would provide more information about how many flights airports can handle, particularly during poor weather conditions. FAA Administrator Marion C. Blakey said the agency would complete the report in early June.

American Airlines and United Airlines agreed to cut back the number of flights into their hub at O'Hare this summer as part of an agreement with the FAA. The agency also has developed "express lanes" of air space near congested airports so planes can take off more quickly.

Delays also are likely this summer at airport security checkpoints because of understaffing of screeners in some cities. Passengers at airports such as Atlanta's Hartsfield-Jackson International and La Guardia already have waited at times from 30 minutes to an hour.

The inspector general called upon the Transportation Security Administration to report regularly and publicly the wait times at security checkpoints for all airports, similar to the way the FAA reports flight delays by airlines.

"This is probably the biggest challenge we've faced yet," TSA spokesman Mark Hatfield said. He urged passengers to check with airlines about how far in advance to arrive at the airport before a flight.