I pulled this from the FCC website:

Licensing

On October 25, 1996, the FCC released a Report and Order in WT Docket
No. 96-82 (text) eliminating the individual licensing requirement for
all aircraft, including scheduled air carriers, air taxis and general
aviation aircraft operating domestically. This means that you do not
need a license to operate a two-way VHF radio, radar, or emergency
locator transmitter (ELT) aboard aircraft operating domestically.

I guess TSA must have a base station. I am not sure what type of
license is needed for hand-held radios.
Someone should contact TSA and find out the details.