Montgomery, AL – Airports in Birmingham, Montgomery, Mobile and Huntsville are boosting their security efforts. The nation's terror alert status was upgraded from elevated to high over the weekend. Jim Walker, director of Alabama's Homeland Security Department, says authorities will search more vehicles and parking areas close to the airports will be closed. Governor Bob Riley has placed extra state troopers and National Guard soldiers at the airports. Federal Homeland Security Secretary Tom Ridge says terrorist attacks are possible, but he's encouraging travelers not to cancel their plans.