OK. Let's talk about the chain of command for nukes...

It's probably POTUS -> SECDEF -> Commander, U.S. Strategic Command -> ...

"Probably" because it's opaque and complicated, though there's no NSA and no Chairman JCS (who aren't in any chain of command). (1/n) https://twitter.com/Schwartzesque/status/1347594221130280961

Because of the perceived possible need to use nuclear weapons very quickly, launch orders don't need to go through every echelon of command. (2/n)

For example, the National Airborne Operations Center (E-4B) reportedly has the capability to send launch orders directly to ICBM silos. (This may even have been officially acknowledged, can't remember).

(3/n) https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104503/e-4b/

So, if POTUS were on the plane, he could presumably skip every intermediate echelon between him and ICBM launch officers. This is by design--in case, SECDEF etc. were dead or unreachable or there wasn't time to consult. (4/n)

Presumably, this reflect a more general design philosophy: that the nuclear command-and-control system must be flexible enough to allow POTUS to bypass some/many intermediate echelons. (5/n)

In any case, being in the chain of command gives you no authority to countermand orders coming from higher up--with the exception that it's illegal to follow an illegal order. This applies to nukes as much as any other operation. (6/n)

This is only a weak safeguard against capricious nuclear use--and it presumably becomes weaker the more echelons are cut out of the chain. (7/7)