Children under 2 years old will still be allowed to sit on their parents' laps when flying on an airplane, the government said yesterday.

The Federal Aviation Administration had considered making safety seats mandatory on planes for small children. That would require parents to buy extra plane tickets, which they do not now have to do for children under 2.

The FAA concluded that requiring the safety seats would prompt cost-conscious travelers to drive, which is statistically more dangerous than flying. Last year, nearly 43,000 people died in highway accidents. Thirteen died on commercial airline flights.

The National Transportation Safety Board and the American Academy of Pediatrics have pushed to require child safety seats on airlines. The safety board's acting chairman, Mark V. Rosenker, said the decision presented an unnecessary risk to children.

"During takeoff, landing and turbulence, adults are required to be buckled up, baggage and coffee pots are stowed, computers are turned off and put away, yet infants and toddlers need not be restrained," Rosenker said in a statement.

FAA spokesman Greg Martin said requiring the seats would harm more children than it would protect.

"A lap child held firmly by a parent doesn't result in second- or third-degree burns like an unsecured pot of coffee," Martin said.

Three children who sat in their parents' laps were among the 309 who survived the fiery crash of an Air France Airbus A340-300 after it overshot the Toronto runway on Aug. 2, Martin noted.

Many airlines offer half-price tickets for child safety seats.

Since 1978, nine children under 2 have died in plane crashes, the FAA said. Three deaths could have been prevented in 25 years if a child-restraint system had been used.

A White House commission report in 1996 said the FAA should require restraints for all infants and children less than 40 inches and weighing less than 40 pounds.