Of course.
So far it's a very dumbed down solution:
Airliners drop in percentage with each flight they make. The only effect is that once the percentage is below 50 you cannot fly to/from Europe or the US. (possibly all countries at the moment, I honestly don't know) This of course is just a place holder to get some dynamics in the game.
You have two options:
-You can manually maintain airliners when you want to. Just click the gear icon in the fleet overview (only visible if auto maintenance is disabled), and the condition will go up.
-Or you use auto maintenance. (this is what I'd recommend at the moment)
It just gives one maintenance each time the condition drops below 50%, to make sure the airliner can keep flying.
The maintenance update is currently in the design phase, so it will get a (big!) update for sure.
But there are many things on our to do list.