FLY A FRIEND FOR HALF PRICE IN THE LATEST AIR-FARE WAR

If you'd like to take a friend along on a flight to destinations in North America or Europe during the next few months, you might profit from the latest air-fare war -- provided you can act fast. On Tuesday, three more airlines -- America West, American and Delta -- matched the special discount that was launched by Northwest on Monday. All four airlines now offer a two-for-one "companion fare" discount. If you travel with someone else on the same flight, the second person can travel for up to 50% off to most cities in America, Canada and Europe. There are a couple of hitches: Tickets for domestic flights must be purchased by Friday, September 30 and must be for 14 days in advance of travel and include a Saturday night stay. The trip must be taken between October 11 and February 15. For European travel, tickets must be purchased by October 7, and travel must be completed between November 1 and March 31. Don't delay; the airlines say seats are going fast.