A plan to allow more daytime flights at National Airport cleared a Senate committee yesterday, even as airport officials and other critics warned that it would bring more noise, delays and congestion to the busy airport.

Sponsors say the bill, which would eliminate federal limits on the number of flights an hour at National, New York's Kennedy International and LaGuardia airports and O'Hare International Airport in Chicago, would encourage airline competition by removing barriers that they say keep smaller carriers from serving the airports and competing with larger airlines.

But critics say the bill could create chaos at National, and airport officials say a $735 million renovation program under way there could be inadequate if traffic is allowed to increase.

"We've had an understanding that certain limitations would be retained, and that National would not be an expansion airport," said A. Linwood Holton Jr., chairman of the airport authority's board of directors. "As a matter of good faith, we should retain those limitations."

For more than 20 years, the Federal Aviation Administration has limited the number of passenger jet flights at National and the three other heavily used airports to prevent excessive delays. Those limits now range from 37 flights an hour at National to 120 an hour at O'Hare.

The FAA distributed landing rights among airlines, which for four years have been allowed to buy and sell these "slots."

The bill approved yesterday by the Senate Commerce, Science and Transportation Committee would eliminate the slot system, which sponsors say has been used by major carriers to keep smaller airlines from beginning or expanding service at the four airports.

"Slots are the biggest barrier to competition in the airline industry today," said Scott Celley, spokesman for Sen. John McCain (R-Ariz.), one of the bill's sponsors, noting that major carriers have priced slots at as much as $1.7 million each.

Critics contend that allowing airlines to bunch flights during the morning and late-afternoon hours -- rather than schedule flights at more regular intervals -- will result in prolonged delays and threaten safety at National.

Although most airline officials have said they support the bill, officials with the Trump and Pan Am shuttles are fighting it, saying that without the slot system they might not be able to guarantee hourly arrivals in New York and Washington.

The Senate is scheduled to recess Aug. 10, and congressional sources said it is unlikely the bill will make it to the floor before then unless it is attached to an unrelated bill. No bill to change the slot system has been proposed in the House.