Neither economic concerns nor terrorist threats stand to interfere with Fourth of July travel plans this year, as an estimated 37 million Americans prepare to descend on theme parks, campgrounds, beaches and resorts over what for many will be a four-day weekend.

Holiday bookings appear not to be affected by the disclosure that the FBI is on heightened alert after intelligence reports indicating that major Independence Day celebrations could be targets of terrorists.

“It’s important to keep everything in perspective,” said Cheryl Mimura, a spokeswoman for the FBI in Los Angeles, where agents have been contacting organizers of July 4 fireworks shows and festivals to get a handle on crowd estimates and security measures. “It’s good, actually, to see that people are getting on with life.”

Las Vegas expects 261,000 visitors and 90 percent of its rooms to be filled in both cases a 4 percent increase over last year. Visitors apparently are ignoring a report dismissed by the FBI from a man who claimed to have overheard a cell phone discussion naming Las Vegas as a terrorist target on Independence Day.

Likewise on California’s Catalina Island, where hotel rooms are booked solid and people are seemingly paying no attention to an uncorroborated report claiming al-Qaida operatives were headed there for the long weekend.

“I think people are just finally tired of it all,” said Rob Powers, a spokesman for the Las Vegas Convention & Visitors Authority. “They want to get away, get out. And it’s a perfect time to celebrate their patriotism, too.”

With the Fourth of July falling on a Thursday this year, many people are expected to make it a four-day weekend. That is anticipated to put the Fourth this year behind only Thanksgiving and Memorial Day as the busiest travel weekend, according to the Automobile Association of America, edging out Labor Day weekend.

The Auto Club estimates that 36.7 million Americans will travel at least 50 miles July 4-7, up from 36.4 million for the holiday weekend last year.

For the summer, 52 percent of Americans are planning to take vacations this year, compared with 48 percent last summer. And many are going whether they can afford to or not.

According to a survey released by AmeriDebt, about 40 percent of this year’s summer vacations will be financed with credit cards and a third of those who plan to use them say they won’t be able to pay off the entire amount when they return.

Because most July 4 vacationers will be traveling by car or recreational vehicle, regional destinations stand to benefit the most, according to the Travel Industry of America.

Air travel, however, is expected to drop nearly 5 percent from last Fourth of July weekend, with 4.4 million people planning to take flights. Post-Sept. 11 jitters, airport security hassles and fewer air fare bargains continue to steer people away.

In contrast, RV rentals and campground reservations for the weekend are up 25 percent and 15 percent over last year, respectively, as people opt to hit the road on shorter trips that are closer to home.