A broken arrow is the loss of a nuclear warhead or a missing nuclear asset lost in transit.
Caspar Phillipson also played JFK in Jackie.
The Russian bomber depicted in this episode is a Tupolev Tu-16 (NATO reporting name: Badger).
The Russian nuclear bomb shown as the "Broken Arrow" is likely based on the real Russian RDS-1 nuclear bomb. It was the Soviet Union's first nuclear weapon tested. The United States assigned it the code Joe-1, in reference to Joseph Stalin.