LOS ANGELES, CA (Catholic Online) - In travel data analyzed by Expedia for The Associated Press, the best time to book for the Fourth of July was between one and two months in advance.

However -- Labor Day, in September, and the rules change dramatically. Those looking to travel that weekend can get the best deal buying three or four weeks in advance. Prices jump 10 percent from their lowest points if you wait 1 to 2 weeks out.

But how can two holiday weekends so close together have such different rules for snagging cheap fares?

Expedia analyst Daniel Kissin says the Fourth of July, although it's more of a popular driving holiday, still gets loads of people in the skies every year. Labor Day, on the other hand, isn't as popular because it usually coincides with back to school.

It makes sense to book in advance for travel-heavy holidays such as Thanksgiving, Christmas and Memorial Day. At other times of the year, it's better to gamble and hold out for that cheaper fare closer to your travel date.

There's an exception to every rule, and ironically - if you want to book a flight to Hawaii, it pays to wait until the last minute for a bargain seat.

Why? Because usually expensive, extended vacations are booked well in advance, and if airlines still have some empty seats before their designated flight times, these fares can be had for very less.

The same could be said about flights overseas to Europe, Asia or other hot spots - so keep an eye out. A cheaper fare might be a few days away.