Remember, the letters of transit are in Sam's piano. https://www.forbes.com/sites/lealane/2017/09/30/new-rule-residents-in-nine-states-will-need-passports-for-domestic-flights-in-2018/#639eb4db6e59
States that refuse to verify that all of their drivers license (DL) applicants are United States citizens: 1. Cannot use their State DL's to board aircraft 2. Must use a passport instead to board aircraft It is per the Patriot Act, which was passed after 9/11. Once all 50 States are in full compliance, then all the State databases will all be fully integrated (or online with each other) -- similar to having a National ID Card. The Americans refused to implement or issue a "National ID Card," so this was a way to achieve that, by creating integrated statewide databases that are nationally accessible with federal standards i.e. citizenship verified, etc. Basically, it's a federalized National ID Card system that uses State databases as its infrastructure. State DL's will be the new "National ID Card" after all 50 States and territories are in full federal compliance with the Patriot Act. Now you know.
https://www.aclu.org/other/5-problems-national-id-cards Five Reasons against National ID Cards and Statement against ID cards by John Wadham, director of Liberty, Apr 2002 https://www.forbes.com/sites/tarunwadhwa/2013/02/06/the-washington-post-got-it-wrong-we-dont-need-a-national-id-card/#13d069863a76 https://www.liberty-human-rights.org.uk/human-rights/privacy/id-cards/case-against-id-cards
The United States actually HAS a federally issued ID card but possession is voluntary. I refer to the Passport Card. Those of us on the border acquire the cards instead of or in addition to a passport book because it's cheap and wallet-sized. The primary purpose of the card is to permit U.S. citizens to re-enter the U.S. by land or sea crossing from Canada, Mexico, the Carribbean and Bermuda. The card is proof of citizenship and so may be used to board aircraft (domestic flights only) or enter federal installations. It is also a List "A" document for establishing work eligibility. Www.state.gov My state has begun issuing REAL ID compliant driver licenses and ID cards but I am dreading the day when I have to renew and get one. It takes a stack of documentation and everything has to agree as to name and address and birth date.