Airlines Hike Lead Time for Cheap Fares : Travel: To get lowest rates, passengers will now have to book flights three weeks in advance, not two.

If you’re contemplating a cheap getaway for Easter or Passover, book those airline tickets fast.

Most of the major airlines have quietly increased the lead time required for buying tickets at the lowest rates. Now, to get the most affordable rates, customers must book flights three weeks before departure, versus the previous two-week standard.

The net result is that you’ll pay more money for tickets if you can’t make your plans at least three weeks in advance.

“The airlines have a basic objective--to improve their yield,” said Edmund Greenslet, a consultant at ESG Aviation Services in Jacksonville, Fla. “This is just another indication that they’re trying to build revenue.”

The airline industry has lost at least $8 billion in the last five years. Now, many airlines are trying to reduce costs and boost their revenues.

Changing the purchase deadline can make a major difference in the price of a ticket. Historically, air fares become more expensive as the travel date nears, in some cases doubling or tripling in cost.

“There isn’t any secret why they are doing this,” said Barbara Beyer, president of Avmark Inc., an aviation consulting firm in Alexandria, Va.

“It’s a business trying to make money.”

Business travelers will suffer most from the changes. Many do book 14 days in advance, but most do not plan beyond that, she said.

The changes will in turn make “it more difficult for business travelers to take advantage of the lower rates” and force them to pay more, Beyer said.

For the leisure traveler, the changes may not be as troublesome, as long as they plan in advance.

Tim Smith, a spokesman for American Airlines, said its studies indicate that most leisure travelers already book 21-30 days before they fly.

In addition, many airlines offer discounted fares that do not require a 21-day purchase. Last year, close to 93% of all ticket purchases was discounted off the full coach fare, said the Air Transport Assn., a Washington trade group.