Millions of Americans travel for July 4th holiday

Airports across the country traditionally see a spike in traffic around the US Independence Day holiday.

The Transportation Security Administration said it expects more than 18.5 million people to travel by air over the Fourth of July holiday and pass through the nation's airport security checkpoints.

For travelers picking up car rentals, July 3 is expected to be the busiest day, according to Hertz. INRIX, which delivers real-time parking and traffic information, said July 2 and July 6 will be the busiest days on the road, with the most congestion starting in the afternoon.