So you know how on avalanche island theres SAMS two of them if you look under them you will see a runway landing in that will get you the ice bay but all the way under at the water there is another tunnel when you fly a plane into it you unlock it try this with the bush plane of P51 mustang
First unlock the location there’s also the dunes down below go down there and unlock it
They will shoot you down even if you haven’t fired once
Go near the sams
AND NEVER