Adrian Shephard likes to think of himself as tough, adaptable, and dangerous. After
his role in the Battle of White Forest, it's hard to disagree with that assessment. However, he's also human, and as a human being he has certain fears and weaknesses. One such fear is of flying. He was never fond of it when he was young, and his Osprey being shot down over Black Mesa made that dislike into a full-blown phobia. That phobia hasn't gone away just because he's had to take up piloting helicopters. It's just stuck around and sat in his head, waiting to be overcome- every single time he gets into the pilot's seat.
Which is a long-winded way of saying that Shephard landed his and Chell's helicopter once the battle was over and bolted straight for the nearest men's room, and stayed there for quite some time. Something weird happened while he was in there, something involving a lot of pain in places that don't normally hurt just because he's being sick to his stomach, and for a bit he was tempted just to stay behind the bathroom door until he got some answers- but since they weren't forthcoming, he opened the door himself.
And found Milliways.
"Well, God-freakin'-dammit, what the hell ass balls."[tinytag: Adrian Shephard, Chell (Portal), Alyx Vance]