Your Money : Thanksgiving Weekend on the Fly: Airlines Vying for 11 Million Fares : Travel: Carriers offer cheap trips and charity tie-ins. Planes are expected to run 80% full Sunday.

Airlines are offering specials and donations to the homeless in competing for the 11 million passengers expected to fly during this year’s Thanksgiving travel crush.

Some 30.4 million Americans will go more than 100 miles from home by plane, train or other transport, the American Automobile Assn. estimated. That would be 3% more than took trips during last year’s Thanksgiving holiday period.

The strong economy and generally lower air fares are enticing more Americans to travel.

“It’s consistent with what we’ve seen all year long,” said James Cammisa, editor of Travel Industry Indicators. “Consumer fundamentals are very positive, prices are attractive, air fares are actually below a year ago and hotel increases are behind the inflation rate.”

Airlines have limited fleet expansion in recent years to reduce the number of empty seats on planes.

The Air Transport Assn. says about 80% of the available seats will be filled on the Sunday after Thanksgiving, when traffic will peak at 1.65 million passengers. So far this year, flights have been 67% full on average.

To attract passengers to off-peak times or routes, airlines are using gimmicks and promotions. They need to fill seats on routes favored by business travelers and on Thursday and Friday flights.

United Airlines is selling some Los Angeles-to-San Francisco tickets at $9.97 one way, and donating the proceeds to charities for the homeless.

On flights between Washington, New York and Boston, Delta Air Lines is offering $50 discounts to passengers who bring non-perishable food items for donation to charities.

Southwest Airlines is offering $25 one-way fares on trips taken between 4 p.m. Thanksgiving Day and midnight Friday.

Northwest Airlines hopes to boost travel on Friday, traditionally the first day of Christmas shopping. The airline is offering fares of $59 to $159 for daytime round trips between 50 cities and the Mall of America, a major shopping center near Northwest’s main airport in Minneapolis.

The Washington-based industry group Air Transport Assn. estimates that airlines will carry 11.13 million people between Nov. 20 and the Monday after Thanksgiving, or 2.9% more than in the comparable period of 1993.

Baltimore-Washington International Airport has added 1,400 parking spaces since Southwest and other airlines started offering cheap flights from there. Traffic has increased 40% and the 14,000-space parking area has been overwhelmed.

Amtrak is adding 60 trains on the Northeast Corridor to accommodate 250,000 passengers during Thanksgiving weekend. The railroad plans to use all its equipment and borrow cars from commuter lines to meet the demand.