Restricted holiday flying.

The New Year 2000 holiday season may be the busiest in the history of travel, according to the American Society of Travel Agents. And to ensure travelers show up for their flights--keeping planes from taking off with empty seats--airlines have kicked in new restrictions. "The major carriers have made all classes of seats, including first-class and full-coach, nonrefundable and instant-purchase for some popular destinations," notes ASTA President and CEO Joe Galloway. On United Airlines, US Airways, American, Northwest and Delta, tickets that are normally refundable will be nonrefundable for travel between December 16 and January 10, 2000.

The restrictions are limited to select destinations, such as New York, New Orleans and Las Vegas. "They're mainly places with planned major millennium celebrations," notes US Airways spokesperson David Castelveter. American is also adding restrictions to the Caribbean and some South American and European cities. But, says American spokesperson John Hotard, it's not the first time airlines have set such restrictions; many did so during the Atlanta Olympic Games. If you're planning a millennium getaway, check to see if your ticket is refundable--before you book.