US Airways began an Internet fare war yesterday on the coveted New York shuttle market by slashing its fares 44 percent.

The airline cut its round-trip fares to $138 from $248. The discounts, good for travel any day of the week, are aimed at travelers who book ahead. Tickets must be purchased 21 days in advance, and travel must include a minimum one-night stay. The discounted tickets are available only on the airline's Web site. The same fares are available between New York and Boston.

By cutting shuttle fares, US Airways Group Inc. is aiming squarely at its biggest East Coast competitors: Delta Air Lines Inc., which also operates a New York shuttle, and Amtrak.

A Delta spokeswoman said the airline would be competitive. A Web search found a round-trip Delta ticket between Washington and New York purchased 21 days in advance was about $141.

The fare for Amtrak's regional train -- $126 round trip -- is slightly lower than US Airways' discounted fares on advance-purchase tickets.

Most shuttle tickets are bought at the last minute by business travelers, who typically pay at least twice the discounted fare.

Separately, US Airways cut its weekend round-trip shuttle fares by 60 percent for this weekend and the next as part of its annual holiday sale. The $98 tickets don't require advance purchase but must be bought at the airline's Web site. Travelers can leave anytime today and return today or by 5 p.m. Sunday.

The discount fares are nonrefundable and exclude taxes and fees.