[Jtsummers]

Except the headline is wrong. TSA is, as a consequence of the REAL ID Act, going to require REAL ID compliant IDs in 2018. These are predominantly state issued identification cards (typically a drivers license). Passports are an alternate, valid ID.

[vijayr]

How does it work for foreigners (aka "aliens" - what a weird term) living here?

[callahad]

Permanent resident cards, foreign passports, and many other documents are accepted in addition to Real IDs: https://www.tsa.gov/travel/security-screening/identification

[mikeash]

Note that this use is the original meaning of "alien." The contemporary meaning of "extraterrestrial" is a recent mutation of it.