I don't think you can save your position. That said, if you're not setting up a full flight plan in advance, you could just do it manually, so starting at LA and flying to Dallas (or whatever), then next time you log in going from Dallas to wherever and so on across to NY.
Since I'm still playing around in Cessnas to get the hang of flying, I did that from San Francisco down to LA, via Monterey, Paso Robles and Santa Barbara, each of which is around an hour, and simply picked up from where I left off. Might at some point do a cross continent flight in the same manner, but would be better probably in the Citation.
Since it's an online and potentially real time game, I understand why there's no option to speed up time. That said, it could be a bit of a weak point for any but the most hardened realists. Certainly for me, I'm unlikely to do any really long flights - doing them in real life back when you could drink your way across the Atlantic as a passenger was bad enough, but can't really see the point of watching my plane autopilot itself for six hours...
But having all sorts of fun with the small planes, and I have been surprised at how reasonably I'm able to land, something that very much eluded me in previous versions of the sim. I'm rarely right on the center line of the runway, but even so I've had quite a few really smooth and gentle touchdowns thanks to watching Squirrel's excellent guides.
Edit:- Well, apparently I'm wrong, there is a way to either accelerate time, or possibly skip phases of the flight... No idea how to do it, but will definitely be investigating.