Killed all the enemies... The heli is just circling and circling and circling and the story isn't going forward, just stuck in an endless loop.

I killed a few of the enemies reinforcements before they got all the way up the stairs. That's my best guess as to why it's stuck. I'll reload an earlier save and try to duplicate it.

Reloaded autosave, tried to duplicate it, didn't work. I have no idea what made it bug the first time around. Still, QA should check it out.