The airline business, already in turmoil as a result of the Sept. 11 attacks and an up-and-down economy, is acknowledging more problems and making a change in course.

Three leading carriers took drastic actions in the past week: US Airways filed for bankruptcy-court protection; American Airlines unveiled a restructuring plan and cutbacks; and United Airlines announced it will file for bankruptcy this fall if it can’t get dramatic cost concessions from its employees and vendors.

Skycaps check baggage for arriving United passengers at Chicago's O'Hare International Airport. United, the nation's No. 2 carrier, said Wednesday it is in danger of flying to an undesirable new destination bankruptcy court as soon as this fall.

The latest upheaval, which will result in fewer domestic flights, has consumers worried about everything from future bookings to frequent-flier miles.

Questions and answers about the effect of the changes:

Q: Is my booking in jeopardy if it’s with an airline that’s cutting back, considering bankruptcy or already filed for bankruptcy?

A: Not likely. A Chapter 11 bankruptcy filing like the ones involving US Airways and potentially United means an airline is reorganizing, not being grounded. If any U.S. airline does stop flying, other carriers are required by law to accept its tickets on a standby basis. As for shrinking schedules, consumer experts recommend double-checking to see if flights or times have changed.

Q: What’s the risk that my frequent-flier miles accumulated with one of the troubled airlines will be wiped out?

A: Low. Frequent-flier programs are one of the airlines’ best marketing tools and unlikely to be suspended even in bankruptcy court. It’s possible they could be tightened to require more miles. Even if an airline goes out of business, an unlikely prospect so far with US Airways and United, a competitor would probably step in and honor 25 percent to 50 percent of the miles to try to create loyal new customers.

Q: Will a cutback in flights mean fewer cheap seats?

A: The abundance of rock-bottom fares may be threatened if the industry has contracted, but it’s still a buyer’s market for this fall, with fares at a 15-year low. Some of the planned cuts in flight schedules by major carriers anywhere from 6 percent to 13 percent among American, United and Delta are seasonal rather than necessarily permanent reductions. And lower-cost airlines that aren’t feeling as squeezed as their big brethren are still offering plenty of cheap deals.

Q: What’s the effect on business travel?

A: Shrinking capacity may cause more inconveniences fewer direct flights, smaller planes, longer connecting times. Experts recommend that business travelers do more homework in planning trips, always have a backup flight in mind, start travel earlier in the day and avoid the last flights of the day, which are generally among the first to be eliminated.

Q: Is there anything I should do differently in planning to book my next flight?

A: Watch for temporary air fare sales and lock in when you see them, in case the best deals do start disappearing. The earlier you can book, the better. Christmas and New Year’s are on Wednesdays this year, which may give travelers more options for arrival and departure dates if they’re off during holiday weeks.

Q: What are the odds of an airline emerging from bankruptcy?

A: Middling. They always come out of bankruptcy smaller if they come out. Continental, TWA (twice) and America West survived bankruptcy; Eastern, Pan Am and Midway didn’t. Says leading airline analyst Sam Buttrick of UBS Warburg: “Sometimes bankruptcy is a roach motel; sometimes it’s a spa.”