"Air Insertion" refers to troops being transported to their objective, and deploying from aircraft, either helicopter of parachute drop.
It usually is referring to heliborne ops. An air insert allows remote objectives to be hit rapidly and without tipping off the enemy, like a ground operation would.
Thanks very much. I should have figured that out, but the reference to this "air insertion" happening in Baghdad threw me off, since I thought these would happen in more remote and inaccessible areas. But what you say applies to any area, and I thank you for the info.