OVA spoiler: Shin's honor guard during the last OVA episode, as he is finally allowed to leave.
In the manga and OVA, the base's reaction to three "Enforcers" HQ sent out to Area 88 to hunt down deserters when they go after Shin for no reason. He was planning to desert, but he changed his mind. Saki gets in on it, too.
Saki's childhood flashbacks of his mother in the manga.
After totaling his plane and finding out it'll cost him $500,000 to replace, Shin tries to desert Area 88 that night and is confronted by mercs who hunt deserters. Just as they get ready to rat him out to Saki, Mickey and all the pilots come to Shin's defense. It's enough to even sway Saki.
In the manga and OVA, the Enforcers weren't going to rat Shin out, they were going to kill him for attempted desertion.