> If they attacked US-flagged ships, to me, it's another indicator they
> got a US OK ...
Not necessarily. They attacked USS Liberty, a US Navy "technical research ship" (euphemism for NSA spy ship), during the Six Days War, killing 34. She had a flag and other US markings.
They claimed not to know who she was; that has been disputed. The US appear to have let them get away with it for policy reasons, not wanting to censure an ally. However, I do not think it has ever been suggested they had prior US permission for that attack.