The Federal Aviation Administration yesterday extended the current distribution of flight quotas at National Airport after the airport's 19 carriers deadlocked over how to divide them.

It was the first time in three years that the agency has been forced to set the allocation of National's 555 commercial daytime airline take-off and landing slots. The stalemate reflected the growing competition among the carriers for access to the airport.

The deadlock came as the airlines and FAA are reevaluating the system that for years has determined how they gain access to National. The airlines are expected today to unveil a new package of proposals for the federally owned airport, including one to allow the purchase and sale of the landing and take-off rights. Those slots are now divided without cost to the winning airlines.

An airline committee charged with allocating the slots declared an impasse yesterday after months of negotiations failed to bring about the unanimity that federal rules require.

It was unclear last night how long the FAA's extension would last. But the period over which the airlines disagreed extended until the end of October. All but one airline agreed to accept their current number of slots. Ozark Air Lines of St. Louis was the sole hold-out, seeking to add two slots to the six it now has.

Ozark yesterday condemned the current allocation system as unworkable and unfair to small carriers. "The existing carriers have made it very clear they will not voluntarily alter their operations to accommodate growth by small incumbent carriers or to accommodate new entrants to the airport," it said in a statement. "Ozark feels the airlines as well as all concerned governmental agencies must acknowledge that voluntary agreement is impossible and . . . move on to the development of an alternative system of allocation which will be responsive to the needs of the community and of all airlines, instead of the favored few," it said.

The airline industry is following developments at National closely because the airport is commonly viewed as a testing ground for new federal policies that could eventually be implemented at airports elsewhere in the country. A buy-sell system for slots, if adopted, could spread to other airports, analysts say, and deeply affect fare structures and levels of service.