Due to spring break, special events and car-rental companies stocking fewer cars due to the weak economy, travelers heading to Phoenix this week without a car-rental reservation may have trouble finding a rental vehicle, or may end up paying extra, reports The Arizona Republic.

The major car-rental agencies are showing no availability on their Web sites or through online travel agencies for rentals beginning March 24 through the weekend. The only rental company showing availability on major sites like Expedia and Orbitz is Fox Rent a Car, where rates start at more than $100 a day for an economy car.

Sky Harbor International Airport last week updated its March travel alert on its Web site to advise travelers to make car-rental reservations in advance. The airport also has volunteers at its car-rental center to direct travelers without a reservation to other options, including two off-airport companies they use as backups, as well as cabs and shuttle services.

March is always the peak tourism season in Phoenix, with spring breaks in cold-weather areas and Cactus League baseball. Add in the West regionals of the NCAA basketball tournament in Glendale and the Phoenix LPGA International golf tournament, both beginning Thursday, and things get even busier.

According to The Arizona Republic, those who were able to secure a car faced long check-in lines, and even some with advanced reservations were not guaranteed to get the vehicle of their choice.