The net losses of $537 million at UAL and $34.8 million at AirTran were wider than analysts estimated, and their shares plunged. JetBlue's loss of $8 million was narrower than projected, as increased sales helped reduce the fuel impact.

Five major U.S. carriers already have reported quarterly losses as the average fuel price jumped 63 percent from a year earlier. Losses for the eight largest may total $1.4 billion, according to a Merrill Lynch & Co. estimate. Only Southwest Airlines Co., the largest low-fare carrier, has posted a profit.

"The outlook for the industry is definitely gloomy," said Dave Swierenga, president of consulting firm AeroEcon in Round Rock, Texas. "The second and third quarters hopefully won't be as bad as the first and the fourth this year."

United, the world's second-largest airline, said it would further pare U.S. flight capacity, cut 1,100 jobs and trim spending by $400 million. New York-based JetBlue and Orlando, Florida-based AirTran both reduced growth plans for the year.

UAL fell $7.80, or 36 percent, to $13.63 at 1:08 p.m. New York time in Nasdaq Stock Market composite trading, the most since the company left bankruptcy in February 2006. AirTran dropped $1.11, or 24 percent, to $3.45. JetBlue declined 37 cents, or 7.5 percent, to $4.56.

Carriers have been adding fees, including charging for specific seats or a second checked bag, and raising fares and fuel surcharges to cope with fuel expenses. Chicago-based United has estimated its fuel costs may rise by $2 billion from 2007.

AMR Corp.'s American Airlines, the world's largest carrier, and Continental Airlines Inc. last week posted quarterly losses.

UAL

UAL's loss was $4.45 a share, compared with $152 million, or $1.32, a year earlier, the company said in a statement today. That exceeded the $3.41 average of 12 analyst estimates compiled by Bloomberg. Sales rose 7.7 percent to $4.71 billion.

The company's shares fell on concern that it may have too little cash to meet terms of loan accords. UAL remains "well above" triggers in its bank-loan covenants including minimum- cash levels and isn't in talks with lenders to amend the terms, Chief Financial Officer Jake Brace said on a conference call.

The 1,100 job cuts, including 500 from management, will come from attrition, retirements and furloughs, UAL said. United will pull 30 aircraft, 10 to 15 more than initially planned in March.

"The path to sustainable profitability requires us to fundamentally overhaul every facet of our business," Chief Executive Officer Glenn Tilton, said in a statement.

The airline also said it will cut non-fuel operating costs this year by $200 million and reduce capital spending by an additional $200 million.

JetBlue

JetBlue, whose largest stakeholder is Deutsche Lufthansa AG, said its loss was 4 cents a share, narrowing from $22 million, or 12 cents, a year earlier. The loss was smaller than the 7-cent average of 13 analyst estimates compiled by Bloomberg.

Sales rose 34 percent to $816 million, helping reduce the impact of the record fuel costs. Still, surging expenses and a weakening economy prompted JetBlue to reduce its capacity expansion target for this year.

JetBlue cut its capacity growth target for this year to 5 percent at most, from its previous goal of as much as 8 percent.

"We are encouraged with the industry's more disciplined approach to capacity," CEO Dave Barger said in a statement.

JetBlue will "aggressively" manage its schedule after the peak summer travel season and may further reduce its growth plans, he said. The carrier's fuel bill for the quarter jumped 62 percent to $308 million.

AirTran

AirTran, which flies mostly in the eastern U.S., said its loss was 38 cents a share, compared with net income of $2.16 million, or 2 cents, a year earlier. The loss was wider than the 32-cent average of 11 analyst estimates compiled by Bloomberg.

Sales increased 18 percent to $566 million, the company said in a statement. AirTran's fuel bill jumped 62 percent to $268 million, prompting the airline to boost its fuel hedges for the rest of the year to cover 50 percent of its needs.

"Despite record revenues, record-high fuel costs remain a tremendous challenge for all airlines," CEO Bob Fornaro said in the statement.

AirTran suspended capacity growth "at least through 2009" and said it won't add 14 new planes to its fleet next year as originally planned.

AirTran's capacity had increased at about 20 percent annually for the past five years. The carrier had reduced its 2008 target to 10 percent, and said today that there won't be any growth in the last four months of the year or in 2009.