For air travelers, the Transportation Security Administration (search) says the new "high" terror threat level means:

-- Increased random vehicle inspections and law enforcement at airports and their perimeters.

-- More officers with police dogs patrolling airports.

-- Parking restrictions.

-- Additional signs and public announcements reminding people to report unattended baggage or suspicious activity.

-- The possibility of long security check-in lines, especially during the holidays. To help keep the lines moving, passengers should remove metal items from their pockets and put them in carry-on luggage, take laptop computers out of luggage for inspection, take off coats and be prepared to take off shoes.

The Federal Aviation Administration (search) advises private pilots to check with the FAA because new airspace restrictions are in place.

At U.S. borders, U.S. Customs (search) officials say the elevated threat level means:

-- Intensive inspections at airports, seaports and land border crossings.

-- Additional identification checks at land borders, and more searches of vehicles and trunks.

-- Increased examinations of cargo.