The best advice of keeping moving has already been suggested, but buy a real book, and maybe a crossword or other such like. Avoid technology.

Sonic 1, 2, and CD have been ported to Android.

For games, my suggestion is that you try a whole bunch of them; get Google Play Pass and, if you have a Netflix subscription, browse through the list of Neflix Games and try anything that looks remotely appealing. None of these are gambling or freemium - they have no way to make money from you except for your continued subscription - and there's something for pretty much every conceivable genre.

If you can give any guidance about the specific sorts of things you like from games (action, story, puzzles, building stuff) I'm sure people can recommend some specific titles.

Uhh, start drinking?

Get a pack of cards and learn some fake shuffles (via YT) then memorize the 673 King Street trick.

ETA a much better performance.

Do you have a library card? Most libraries allow you access to the Libby or Cloud Library or Hoopla apps, you could read a book or listen to an audiobook.

Maybe learn how to play chess?

Buy books? 20 hours man, I could burn through at least two.

Twist your thumbs

you can't kill an idea

Try Monument Valley it's a one time pay puzzle game that moves like an MC Escher sketch.

No advice, but I sympathize. I once sat listening to music while waiting for my flight to board. When there was no activity and fewer passengers in the area than I expected, I discovered that while I had been waiting they changed the gate for my flight. I ended up waiting in Chicago Midway (this was before their big upgrades in the early 00s) for 12 hours. It was hell.

Do you like Roguelikes? Slay the Spire is really good and it's on Mobile.
It's a port from PC, so no microtransactions or garbage like that, one purchase and done.
There's also Mindustry. It's a mix between Tower Defense and Factory game. This one also has no MTX since it is a Open Source game. Free on Android, 2 Bucks on iOS.

I would say get a hotel room, but it has uh, been 6 hours since you posted this so…

I wouldn't get wasted, if you're in your 30s that can give your worst headache ever. If the wifi is good enough, maybe start a series? Possibly something with short episodes, a well-selected anime will easily kill something like 10 hours. And if possible, try to get as much sleep as possible

There are very good mobile games without subscriptions, virtual coins, loot boxes and shit. Some examples on iOS:

• Sawblades
• Ollies Arcade
• Knotwords
• High Rise

You could watch The Terminal 9 times back to back, and have just enough time left to be disappointed by some overpriced meal at the Wolfgang Puck.

I know you mentioned audiobooks but what about some digital books? Personally, reading makes my eyes tired so I know that, for me, reading something would be a good way to provoke a nap.

As a response to the idea that you may get fatigued by passive media, a book may be a good balance to that. With movies, shows, and audiobooks, you're going to be listening the whole time. It's just constant noise. A book may be more meditative.

Which reminds me, this may be a good time to practice meditation.

It may sound stupid, but try learning some card tricks or play solitaire with some playing cards?

Vampire survivors and random lore vids.

It's a damn shame that you can't go to a pharmacy in the airport, tell this tale, and get some xanex to zonk out and time travel to your destination.

If its your thing try kearning a language on Duolingo or something like that

Unsure of your preferences with games, but Shattered Pixel Dungeon is free, offline, no ads, and the only purchases are for aesthetics to support the app. It's an 8-bit rogue like, and never the same game twice.

As for android games, if you're into tower defense, give infinitode a try :)

It's not gonna last you 20 hours, but last I checked the official Sonic 1, 2 and CD ports are all free on mobile (and they're really good).

The most addictive and a complete experience in your pocket kind of game is Crashlands. It's amazing if you're into games where you have to craft things to survive. Definitely recommend giving it a try.

I highly recommend emulating games on your phone. Some of them aren't great without a controller but its worth a shot.

Puzzle books? I like to play with variety puzzle books, commonly sold near magazines :3 Crosswords (and varieties thereof), word searches (+varieties), crypto puzzles of various sorts, number puzzles of various sorts, the funky neat ones where some of the words share some letters (like, a letter fills a vertical region to be shared by one or more words), uhhh... oh also I like to write the solutions in Thorass :D https://forgottenrealms.fandom.com/wiki/Thorass_alphabet Though the numerals are garbage. D'ni numerals are far, far better 👍

Also, I daydream for hours at a time. ... But probably you don't or else you wouldn't be asking for ideas I guess 😅