Airline travel is the worst -- except for when it's the best. 

The idea that you can travel between any two spots in the country, or the world, within less than a day -- it's amazing. But for some people, usually due to financial reasons, it's out of reach.

Meet: United Airlines passenger Peter Shankman's who started an annual holiday tradition a few years ago that has grown and grown with each iteration -- and makes lots of people happy in the process.

Shankman is an entrepreneur and podcast host, and he travels the world giving speeches . He's also a single dad living in New York. 

He earns a huge number of frequent flyer miles each year, usually between 200,000 and 350,000, mostly through United Airlines. With all that time away, he says, the last thing he wants to do when he has a break is to travel some more.

So, he winds up with huge unused caches of miles each year. Which in the grand scheme of things, aren't super-valuable to him. 

But what he can do with them for other people who desperately want to travel for the holidays, but can't afford to, is priceless.

Starting in 2013, he's spread the word that he's willing to give away hundreds of thousands of frequent flyer miles to people who want to use them to score a trip home for the holidays. As he wrote on Imgur:

"I'm not rich, I'm not famous, but I do have one unique resource at my disposal. All my travel means I have a LOT of frequent flier miles. Like, a LOT.  And the last thing I want to do with all those miles is when I'm finally home is actually go somewhere.

But there are only so many times I can give a free flight to my assistant and her boyfriend or my parents."

After choosing the people he wanted to help on his own in the first year, with the help of an assistant, Shankman decided that was just too hard. So now he uses the community at Imgur: people describe where and why they want to go, and the posts that get the most upvotes win.

Even better, other frequent passengers who also accumulate a lot of miles have started to pitch in each year, offering their own miles. And the whole story has gone viral, covered in major media and becoming the top-ranked post on Imgur repeatedly.

(Of course, now he's in Inc., so it's hard to see how he could top that.)

In 2018, Shankman said he's donating about 200,000 miles, and other passengers are offering more than an additional 100,000. Beyond that, USA Today reports that United Airlines also decided to donate 200,000 miles to the charity of Shankman's choice.

Among this year's travelers:

  • a Texas woman whose grandfather is dying from cancer, and who wanted to fly to see him in New York one last time.
  • a Los Angeles couple who wanted to travel to Utah so be with their 30-member family for Christmas.
  • two brothers who wanted to spend the holidays with their mother.
  • a woman who has Parkinson's disease and who wanted to fly to Georgia to place flowers on her son's grave.
  • a Kansas man who wanted to fly to New Hampshire to surprise his ailing parents.

"I truly believe that if you've had any modicum of success, you have a responsibility to 'send the elevator back down,' as it were," Shankman told USA Today. "Giving away trips home for the holidays to people who might not be able to afford them is the best way I know how to do that. Secondly, it's a blast to teach my daughter about giving back."