a) "breaking formation" isn't an idiomatic phrase. Military troops, planes, ships, tanks, etc. go into a formation, e.g., while traveling. Whenever they then leave the formation, e.g., because they are under attack or because they are about to attack, they "break" formation.
b) "Coming in hot" can mean a variety of things, one of which is being ready to fire weapons. It could also refer to a damaged plane (or other vehicle) attempting to land (or to make some other sort of arrival) without full control of propulsion, steering, or braking systems.
Gee, italtrav, that's heady stuff! And I'm a sucker for constructive criticism...
So, if "breaking formation" is not an idiom, why did you put "break" between quotation marks?
And what translation would you then recommend, seeing as you're an authority on these matters?
I put "break" into quotes to indicate the term that I was discussing at that point. I didn't call it idiomatic because it is an ordinary use of the term—most anything in English that is put together may be broken apart—but I'm aware that I used the narrower meaning of "idiom," which indicates a more specialized or non-obvious expression, e.g., to break a news story, to break bread (meaning, to share a meal with someone), to give someone a break. I'm not sure of a translation into Italian, as I have no idea what Italian military pilots say when they see an enemy flying in formation and then abandoning the formation as prelude to an attack. From the limited context, I'd say that "coming in hot" here means "about to fire," but I don't know that "stanno per tirare" has much flavor to it.
While we're at it—I'd love to see a list of Italian military commands, starting with those used to give orders for marching, like the ones here on Wikipedia: http://en.wikipedia.org/wiki/Drill_commands. I've looked around a little on threads here, but I didn't see much of anything.