Emulating Gamecube games is pretty low-spec if you compile the shaders beforehand. Battery life nets 2-3 hours on flights for me (Steam Deck). I have nearly 2000 hours of Animal Crossing GC combined, pls don't judge me 😅.
Check out Celeste if you haven’t already. For me it’s the perfect 2D platformer and works really well on the deck. Think I clocked around 100 hours on it just on it alone!
Most planes nowadays have a charging port where you can plug in your phone for the duration of the flight. Therefore, I recommend getting an emulator on your phone and playing games on it. Usually if I want something casual, I get an NDS emulator and play Pokemon Platinum or HGSS. Other recommendations are FFIV, Etrian Odyssey III, Shin Megami Tensei, DQ4, some of these are ports but they run well on DS emulator.
My personal experience (US) is that most airplanes have chargers nowadays. However, the charger is very loose, and I could never make my charger fixed in the socket.
If OP could find a good socket, then this lucky person could enjoy 5 hour gaming with no interruption :)
I might be talking out of my arse, but you could bring a toothpick with you and try removing any fluff/grime from the socket before plugging in. Worked for my phone when the usbc charger wasn't secure.
I haven't tried this personally but maybe if you use a short extension cord it would work better? This should remove the weight of the DC adapter pulling on the connection to the outlet
Bastion, Celeste, Hollow Knight, and Tunic are all great. I also really like emulation. I've been playing Tears of the Kingdom more on my Steam Deck than on my switch!
If you prefer some story-heavy games, you can try Eastward. It has gorgeous art style and controls and UI are a great fit for handheld devices such as Deck and Switch. It takes ~15% battery a hour and can be completed in 10 to 15 hours.
If you're fine with longer games which will take 45-70 hours total, try some 2D JRPGs like Trails in the Sky FC (which also has nice touch input in menus!), Trails from Zero and Chained Echoes. All tree aren't battery-heavy at all.
Dunno if it's your jam, but I just picked up Dead Cells and it's super light weight power wise. Also, retro emulation is usually pretty good on the battery. Get Emudeck going and some GB or GBA games and have a blast.
Tough to give anything concrete without preferences but I'll toss out a few. Chronicon is a great ARPG that's easy on the battery due to simple graphics (don't let them fool you). Voxelgram is 3d picross, if that happens to be your thing. Dicey Dungeons is a dice based roguelite that's totally full of charm.
Star Traders: Frontiers on Android. Space trading rpg with depth and story. A bit grindy bit there's so many paths to take it can suck up hours (mind you it's difficult and you will die permadeths with many characters, it's mind boggling how many ways there are to succeed, just many more ways to fail too. Great way to spend a five hour flight.
If you like 2d platformers, I can recommend Swordigo for android. It's old and free and it is long enough that a 6 hour flight will only get you halfway through. It has some challenging but not impossible boss fights and trick jumps.
Can’t figure out how to edit comment from Memmy App (iOS) so replying instead. Get yourself a pair of Rokids or Xreal glasses for a more immersive experience on the flight.
Memmy app now has notifications so I just saw this. Steam Deck / Steam controllers work with any game. Satisfactory doesn’t have controller support but I’ve never felt I needed it as I have fully customized my controller experience thanks to Steam Input. If you bought on Epic you can still use Steam Input by adding it as a non steam game and launching from Steam.
If you haven’t already bought it immediately because of the gut punch of nostalgia then maybe it isn’t for you, but I have to recommend Megaman Battle Network
Emulated systems such as GameCube or psx work well on a long flight and you can have a lot of roms to suit the mood and can keep the tdp fairly low. Like 5 or 6