* American, Southwest top expectations as JetBlue trails
* United posts wider loss
* Carriers say key revenue measure to rise in current period
April 24 (Reuters) - American Airlines Group and Southwest Airlines posted profits that beat forecasts in the first quarter, even though harsh winter weather prompted many flight cancellations in the seasonally weak period.
JetBlue Airways disappointed as wage increases raised its costs. United Continental Holdings posted a wider loss as revenue fell.
All the carriers said revenue in the current period was looking up.
Warmer weather should encourage more leisure travel in the current quarter, airlines said, boosting second-quarter unit revenue, a key measure of pricing power and how full planes are. United said it expects unit revenue to rise 1 percent to 3 percent in the three months ending in June, while American forecast a rise of 4 percent to 6 percent.
Southwest, which benefited from higher fares and lower costs in the first three months of year, said the second quarter was "off to a great start," citing strong April bookings and revenue trends. It forecast a 6 percent to 7 percent rise in unit revenue for April..
"The demand environment is healthy heading into what should be a very strong spring and summer travel season," said Jim Corridore, an equity analyst with S&P Capital IQ.
Share prices reflected the results. American was up 2.2 percent to $37.91 on Thursday and Southwest gained 0.8 percent to $24.27. United sank 9.3 percent to $41.78 and JetBlue was off 2.9 percent to $8.34.
Henry Harteveldt, travel industry analyst and founder with Atmosphere Research Group, said United Continental needed to make improvements. United has been working to win back customers after system changes it made after its 2010 merger hurt customer service.
"It's clear that weather aside, United is not offering a product that travelers like and is losing market share," Harteveldt said. "While United has made some improvements, it's still not strong enough."
United's first-quarter loss was $609 million, compared with a year-earlier loss of $417 million. The company said during a conference call that it was taking actions to improve revenue that include better matching plane size to flight demand, and added it expected domestic unit revenue to rise 4 percent to 6 percent in the current period.
American's first quarter results were aided by proceeds from sales of takeoff and landing rights at Reagan National Airport near Washington it had to make under an agreement with the U.S. Justice Department. Harteveldt said American and Delta Air Lines were "firing on all cylinders," keeping costs under control and garnering more revenue from premium travelers.
Delta on Wednesday forecast stronger than expected operating margin and unit revenue increase for the second quarter, sending its shares to a new year high above $37.00. On Thursday, its shares were up 0.6 percent to $37.30.
(Reporting by Karen Jacobs in Atlanta)