Ryan intends to kill himself.
"The stars will wheel forth from their daytime hiding places, and one of those lights, slightly brighter than the rest, will be my wingtip passing over."
The 'wingtip' is not a plane's wing at all but an angelic one. In the final shot we never see a plane, or Ryan looking out a window or anything like that but simply the clouds from above.
Ryan's family has moved on without him. The upstart kid that he mentored now has a permanent job in San Francisco. The one woman he thought he could connect with on a romantic level turned out to be married with kids. His primary life goal has been reached and he's stuck in the exact same job that he's been doing for years while everyone else is moving on. His entire life's accomplishment is essentially a plastic A Advantage
card. In a way, the movie can be compared to The Wrestler
Ryan will confront Alex's husband about their affair.
He would not have gotten over it, and even though he knows her husband could kick his ass, he'd take his chances.