Free landing and takeoff rights at National Airport have come under fire from the Federal Trade Commission staff and the Justice Department.

Officials from the two agencies this week called for a "market approach" toward determining which airlines can serve the busy airport, suggesting the right to operate flights there should go to carriers willing to pay the highest price.

Landing and takeoff rights--known in the aviation industry as "slots"--currently are free at federally owned National, with airlines deciding among themselves who gets them.

Justice Department officials argued in a brief submitted to the Civil Aeronautics Board this week that the current system is anticompetitive, inefficient and "allocates scarce resources without imposing a price on their use."

The Justice Department and the FTC staff also called for sale of slots at LaGuardia and John F. Kennedy International airports in New York and at Chicago's O'Hare International Airport, the only other U.S. airports where heavy traffic has led to permanent slot systems.

Their comments were the latest round in a years-old battle over how slots should be allocated--a fight that in recent months has pitted members of the Reagan administration against one another.

Last December, Office of Management and Budget Director David Stockman called for a slot auction at National, which is operated by the Federal Aviation Administration. His call was firmly rejected by then Transportation Secretary Drew Lewis, who cited financial hardships on airlines that had already been hit by the recession and the 1981 air traffic controllers' strike.

The Air Transport Association, which represents the major air carriers, also has opposed the sale idea. "We think that it drives up the cost of air travel and it puts the smaller carriers at a disadvantage," association spokesman William Jackman said.

Currently, National's 555 daily airline slots are divvied up by a committee of airline representatives. Members agree how many slots each will get, with federal officials stepping in if there is a deadlock.

The Justice Department's statements came in comments submitted to the Civil Aeronautics Board following a request from commuter airlines at National to set up a new scheduling committee. Formation of such committees require antitrust immunity from the department.

The department called for dissolution of all scheduling committees, saying they are by nature anticompetitive. The present system lets individual lines directly influence the business of rivals, the department maintained, and tends to preserve the status quo of slot distribution regardless of how well an individual airline performs.

"A better system would be to allocate slots in accordance to carriers' willingness to pay for them," the report said. This might be done by having the FAA auction slots to airlines and by letting airlines buy and sell among themselves slots already obtained.

The report rejected criticism that sales would let large airlines monopolize airports and keep smaller competitors out. "Slots will go to the carriers that can use them most efficiently and profitably," the brief said.

A FTC staff report released this week made similar points. A market system would help airlines break into new routes, enhancing competition, it said. The current system, it said, fosters inefficiency and is costing consumers and the FAA tens of millions of dollars a year.

The report was released but not endorsed by the commission.

In a separate statement, commissioner Michael Pertschuk said the study "leaves unanswered a number of significant questions" about the effects of selling slots to the highest bidders.