If your passport is expiring soon, get ready to wait - perhaps for a long time. Beginning in 2017, the wait time for renewal could jump to as much as 10 weeks or more. Now, it takes four to six weeks.

Triggering the long delays will be an expected surge in passport renewals starting in 2017 and stretching through 2018.

An improving economy, cheaper airfares, and more disposable income also may spark overseas travel and create a logjam at the passport office, the U.S. State Department predicts.

Hordes of people obtained their passports in 2007, when new rules required U.S. citizens to have passports when flying to and from any international destination. In 2009, that rule was extended to U.S. and Canadian citizens reentering the U.S. by land and sea.

More than 18 million U.S. passports, many good for 10 years, were issued in the 2007 fiscal year - 4 million more than last year.

To avoid the crush, now is a good time to apply for both first-time passports and renewals, the State Department says. September to December is the slowest time of the year. The Miami passport agency, for example, serves up to 500 people on any given day, and its peak months are March through August.

The office is one of 29 official passport agencies in the U.S. and Puerto Rico, and it generally processes only expedited and emergency applications. Some people with last-minute travel plans camp outside the passport office in hopes of getting on its waiting list.

According to Ryan Dooley, director of the Miami and San Juan passport agencies, applying early also makes sense for another reason: Many countries require a passport to have at least six months of validity remaining as a condition of entry. A passport expiring in June 2016 could technically not be valid by January, Dooley said.

"The more people apply in advance, the more convenient and cheaper and less stressful the process will be," he said.