Besides, does American Airlines provide hotel for overnight layover?
ButAA doesn't provide anything (hotel/meals) for a 15 hour scheduled layover anywhere, unless you have club access for od, based on status or class of service. I can't think of too many airlines that will provide you with accommodations, etc. on a connection of this length, unless a few do for premium fares.
Beside above, what happens when you have an overnight layover? If you do have an overnight layover and will be spending the night at the airport, remember your options. You can stay in an airport hotel both within transit or on the public side, you could sleep or rest in the airport terminal itself.
Secondly, can you leave the airport during an overnight layover?
For most layovers, you can leave the transit area (and airport) in between flights, as long as you have a visa (if necessary) and go through customs and immigration on the way out, and of course you'll have to pass through security again on your way back into the airport.
Does Turkish Airlines provide free hotel for long layover?
But lucky for us, Turkish Airlines does a good job of taking care of their long-haul passengers. That's right, Turkish Airlines will provide you with a free hotel room (up to two nights) if you have an extended layover in Istanbul. And it's not just for business class passengers.