Well, when the choppers come in to drop off yet more enemies, I run over to the wall on the left, grenade the cars just in case, snipe 2 heli's worth of drop-ins, AK the 4th set, then just spam with the 'K until Big Bird arrives. Works 9/10 times, occasionally I'll be back attacked. When BB sets down, i strafe over to Macmillan, and get killed while picking him up because the AI in BB are a fat load of uselessness.
Also, the Mile High Club, is it always 1min on Veteran, or is the time related to campaign progress? I can't even get to the stairs half the time without dying or running out of time...