The Transportation Security Administration (TSA) says it is legal to record TSA checkpoints inside airports.
The TSA website states:
TSA does not prohibit the public, passengers or press from photographing, videotaping or filming at security checkpoints, as long as the screening process is not interfered with or slowed down. We do ask you to not film or take pictures of the monitors. While the TSA does not prohibit photographs at screening locations, local laws, state statutes, or local ordinances might.
An unidentified man recently filmed a TSA checkpoint (below) with two cameras, one of which was strapped to his head, at the Hartsfield–Jackson Atlanta International Airport, noted PhotographyIsNotaCrime.com.
He was questioned by Atlanta police and a TSA manager, who asked him several times why he was filming, to which he replied "personal use" and "civilian oversight."
After being grilled several times about his legal recording, the man was apparently shaking and was asked several times by armed officers why he was shaking.
The man also showed the same female police officer his boarding pass three times.
Apparently frustrated by the man's knowledge of his legal rights, the TSA eventually closed down the checkpoint, but he was questioned again in another area of the airport.
Sources: TSA.gov and PhotographyIsNotaCrime.com