So, I've got 12-18 hours each way, if you count layovers.  Recommend me a game for my trip!

I was thinking Civilization: Revolutions or some other strategy or RPG.  Recent or old/used is fine.  And of course, no mic usage.

The Trauma Center games are really fun. If you don't have pokemon those games are ok. Mario Kart is a must try though I love it. I also think the Advanced War games are fun. They will fill your hours. Oh but I also highly recommend The World Ends with You. Great game.

If you like Strategy you cant go wrong with Advance Wars.
Also, for long replay value i always choice puzzle games. Puzzle Quest is Great, so is Meteos, and of course Tetris. New Super Mario Bros is also a good choice. Fun game to play, and a must, in my opinion, in any DS collection. 

Patapon is the way to go.

If you don't have a PSP, then puzzle quest is awesome

Thanks all, keep em coming. 

I've already got most of the games mentioned here (the puzzlers), and while I can indeed keep playing them, I'm looking for something new.  I like advanced wars a lot, but haven't gotten the newest one so that may do the trick.  And I don't have The World Ends With You.  Basically nothing since Puzzle Quest / Final Fantasy III.

ps. "looking for something new" meaning new-to-me... like i said it can be an older game I overlooked

Tetris DS is an easy recommend for a long flight, Ace Attorney games are basically like playing a book (in an entirely good way, I assure you), Space Invaders Extreme is only 20$ but that's really only for you if you're a fan of Space Invaders.  Professor Layton is also great if you're patient and able to think outside of the box.  Good Luck!

Ace Attorney is a good one.

I would say Professor Layton, but... I don't know. I could see myself getting frustrated and sick racking my brains for each puzzle. It is a definitely fun game overall though, but you'd need another game to take a break with.

I would second advance wars, should fill in the time.

Final Fantasy Tactics A2!!!

"So, I've got 12-18 hours each way, if you count layovers.  Recommend me a game for my trip!

I was thinking Civilization: Revolutions or some other strategy or RPG.  Recent or old/used is fine.  And of course, no mic usage.
"

Tokyo, as you probably expected from a game site.  But I'll be going all around the country, so there'll be many travel times and I may need the DS for some of them.  Luckily it's region free, so perhaps something will be out there earlier and I can pick it up.

Ok... so it'll be a choice between FFTA2 and AW... I'll see if either are selling used at the local store.