“Sir, are you alright?” The woman in a gray blazer who had been walking behind him asked, worry written plainly across her face.

The line in front of them moved forward. The man she had spoken to stepped ahead from his spot and answered in a detached tone, “I’m fine.”

Apparently, she was not the only one paying attention to him. Another man, traveling with him on that commercial flight for business purposes, was also watching. He stood farther back in the line, a little distance ...