Ok, I'm not a flight nurse, but I'll give it a try....
First things first, confirm tube placement, check for thoracic trauma, & get another set of vitals.
With the battle's sign, I'm suspecting posterior cerebral trauma or hemorrhage, possible posterior skull fx. Mechanism of brain injury, from the jarring motion, would most likely be coup contra coup, so I might also suspect a frontal lobe injury (raccoon eyes might not have shown up yet).
En route to the the trauma center, I'd be watching for a drop in BP, which I'd manage with crystalloid, O Neg, &/or pressors.
So, how'd I do? Am I ready to take flight??? Too bad I'd probably vomit if I ever found myself in a helicopter!