UPDATE 3-ATA Airlines files for bankruptcy and shuts down

(Adds pilots' reaction, other airlines' help)

By Mark McSherry

NEW YORK, April 3 (Reuters) - ATA Airlines Inc said on Thursday it filed for Chapter 11 bankruptcy protection and shut down all operations after cancellation of a key military charter agreement.

The Indianapolis-based low-cost airline and its rivals have recently been hamstrung by big increases in jet fuel prices. ATA is the second airline to file in the past few weeks.

The fuel price spike, coupled with a steadily weakening U.S. economy, has stalled the airline industry's modest recovery from the 2001-2006 downturn.

On Sunday, less than two weeks after filing for bankruptcy protection, Hawaii-based Aloha Airlines said it would shut down its passenger operations.

Big airlines are beginning to shrink to cope with toughening operating conditions. On March 18, Delta Air Lines Inc (DAL.N: Quote, Profile, Research, Stock Buzz) unveiled plans to cut 2,000 jobs and scale back flights.

Carriers have also moved to pass along fuel costs to travelers via higher fares and surcharges. Some airlines have opened new revenue streams by charging for products and services that previously had been included in the ticket price.

Oil prices CLc1, which are directly related to jet fuel costs, remain above $100 a barrel.