[rmlew]

Why didn't Israel arm the planes properly (ie rockets, and armour piercing bombs), paint the planes with the UAR insignia instead of the Star of David, and have the pilots chatter in Arabic?

Either Israel was horribly incompetent at war while competent in cover up, or it was an accident.
Occams razor says accident.

[archy]

Why didn't Israel arm the planes properly (ie rockets, and armour piercing bombs),

The torpedos were thought to be enough to sink the Liberty, and the Napalm from the aircraft and 20mm explosive rounds fired from the patrol boats into the survivors on deck and to shread the liferafts were clearly meant to ensure that the crew wouldn't be around afterward to dispute the Israeli version of the *Arab attack on the Liberty.*

And of course, the cannon fire to the bridge was probably a deliberater attempt to kill the Captain and as many officers as possible.

-archy-/-