Domestic airlines on Monday cut their summer ticket prices by as much as 20 percent and said children can come along for half-price.

Northwest Airlines started the fare promotion over the weekend. American, Continental, Delta, United and USAir matched it on Monday, making it the first widely adopted fare cut since March."We're trying to stimulate travel as much as we can for the summer period," said Northwest spokesman Doug Miller. "As we were looking out at our advanced bookings for summer, they were just slightly below where we hoped they would be."

Under the promotion, a round-trip ticket between Chicago and New York would cost $278 during peak hours and $238 during off-peak hours. A child could accompany that adult for $168 or $118.

Off-peak travel generally is defined as noon Monday through noon Thursday. Peak travel is noon Thursday through noon Monday.

The offer extends through May 31 for travel through Sept. 8. The non-refundable fares apply to round-trip flights with reservations made at least seven days before travel.

Children 17 and under must be accompanied by an adult for the half-off fare. A Saturday night stay is generally required.

The offer is aimed at families trying to decide between driving and flying for summer vacation or whether to make a trip at all, Miller said.

"It's a fare that will have a lot of emotional appeal," said Jessica Tully, analyst for the Principal-EGT brokerage house in Dallas.

Domestic airlines are trying to lure more passengers in an effort to raise revenues and return to profitability. The industry lost nearly $4 billion last year, a record, as carriers were assaulted by the recession, higher jet fuel prices and a loss of passengers stemming from the gulf war.

The major airlines also suffered losses in the first three months of this year, and analysts expect they may break even in the second quarter if they can beat the recession and generate more revenue.

The airlines had hoped to boost ridership in March, as American Airlines led one summer fare war designed to stimulate travel. That promotion, which expired in early April, raised bookings in April, May and June but did less for July and August, said American spokesman Tim Smith.