How a frequent flier's viral post saved Christmas for this father and son.

Quentin Seyssel has only seen his 5-year-old son, Aiden, four times this year.

Aiden and his mom have been living with her parents in California since March 2015, although she and Quentin didn't officially get divorced until this past summer. Being away from his son is hard, especially since Aiden is on the autism spectrum and has only recently begun to communicate with purpose.

Due to financial constraints, Quentin lives a humble life in Colorado and sends as much money as he can to his son every month.

The physical distance between them is difficult, especially this year, because it's the first Christmas the two would've spent apart.

The two communicate most frequently via Skype, but it presents challenges, Quentin explains. "Within the last year, [Aiden] has gotten a lot more used to initiating play and will bring you a puppet to use and mimic a conversation with."

That's not something he can do over Skype.

Though Quentin tries to ask his son questions and engage with him on their calls, he is often left watching Aiden play quietly.

While Quentin would love to see his son in person, "it is financially difficult," he writes. This year, even though he does have holiday time off work, he cannot afford the round-trip ticket.

In a last-ditch effort, Quentin responded to a post online in which a man named Peter Shankman was offering to use his extra airline miles to help people who needed them to get home for the holidays.

In his job as a marketing consultant, Shankman has racked up a significant number of airline miles. For the past four years, he's been gifting them to people — like Quentin — who can't afford trips to see their loved ones around the holidays.

"I get to travel to talk for a living and get paid for it," explains Shankman in an email. "I don't know how much luckier I could be. How could I possibly live in a world that gives me all of that happiness and not find a way to give back?"

So every year, Shankman sets up a post on image-hosting website Imgur asking users to share their story in the Home for the Holidays category. The people whose stories receive the most upvotes from other users get a ticket home with Shankman's miles.

This year, Shankman was joined by generous travelers who donated their own miles to the cause, helping to send 10 people home for the holidays.One is a teacher with a rare eye disease who will get to visit her family after years apart; another is an Air Force pilot with HIV who will be able to go home and make amends with his estranged family.

In response to Quentin's story, several other users stepped in, offering to pay for his flight home to Aiden.

Quentin decided to take one of those offers, so that Shankman could use his miles for someone else in need. "He seemed genuine, kind, and never asked for anything in return," writes Quentin of the user whose offer he accepted. "Only the promise to pay it forward."

Quentin wrestled with feeling worthy of the free trip home and thinking about how many others might be more deserving — but then he thought about Aiden.

Quentin knows Aiden needs his father around, especially at this crucial stage of development in his life. He's making plans to move to California so they can spend more time together. Until then, he's been writing letters to Aiden every year on his birthday and plans to give them all to Aiden when he turns 21.

"I would give anything for [Aiden]," Quentin writes. "I never want him to feel a hole in his life where his father should be."

Thanks to the generosity of a stranger on the internet, this year's letter will be filled with some extra joy and humility — "a highlight of memories and hope," he says — and memories of a visit home for the holidays.