If you have visual identification of the jet, can see it isn’t carrying weapons, and don’t detect any electronic emissions suggesting there was a missile lock on the ship, there’s nothing to be done.

And ultimately, the the rules of engagement put the CO in charge of how to respond.

“You don’t get to kill people just because they’re being annoying,” said Hoffman, who commanded frigate DeWert and cruiser Hue City. Cruisers are the fleet’s foremost air defense platform and are tasked with guarding flattops from incoming threats.

http://www.navytimes.com/story/military/2016/04/13/why-navy-didnt-shoot-down-russian-jets/83000858/