American will add domestic and international flights from La-Guardia and JFK airports over the next six months starting in April, boosting yearly departures by the ariline and its American Eagle commuter carrier by 4,060 flights, or 2.3%.

"For American, it is very important," Ray Neidl, an analyst at Ca-lyon Securities.

"They have a firm position established with their international and domestic service.

"If they want to protect it, they're going to have to grow it."

The expansion by American, the world's largest airline, will also ramp up the competition for travelers with rivals Delta and Continental.

American, which plans to complete a $1.1 billion terminal this summer at JFK, where JetBlue is the largest carrier, said it would add new and additional service between Las Vegas, San Francisco, Atlanta and other cities.

Continental, which flies to 77 international destinations from Newark Airport, is the largest carrier in metro area.

During the past 12 months, Continental flew an average of 45,985 seats per day out of the three main New York airports.

American averaged 29,122 seats, while Delta flew an average of 28,551 seats, according to figures provided by Continental.

In January, Continental said air fares in the New York area would come under pressure as it defends its Newark hub from competition from JetBlue and others.

JetBlue has said it will pay out about $26 million in refunds and travel vouchers after it stranded passengers aboard grounded aircraft and canceled 1,200 flights after last week's ice storm.

American's plans in New York - especially the new service to Las Vegas - could be a further thorn in JetBlue's side, but American also stranded passengers on planes for hours in December when storms in Dallas diverted some flights to Austin.

Shares of American's parent company, AMR, were down 65 cents yesterday to $37.88, while JetBlue lost three cents to $13.16.