American Airlines now allows passengers to check bags to their final destination even when their connections are exceptionally long. They used to only allow bag checks all the way through on connections under 12 hours. That’s now been increased to 16.5 hours, and this new rule applies not just to American Airlines travel, but also when checking a bag in with American Airlines and connecting onto one of their airline partners.
That means passengers on very long connections, such as short overnight connections, won’t have to collect their bags at their connecting city, and then re-check in those bags the next day. And it may save some passengers from having to pay a second bag fee.
Twelve hours is a common rule. I once had to ask for an exception from Thai Airways on a 14 hour overnight connection during a weeks-long trip, where I had everything I needed in my carry on and didn’t want to deal with my checked luggage. They made the exception for me as a first class passenger, but it wasn’t policy (and I worried about the bags just a little bit).
It used to be though that a 12 hour connection would allow you to short-check a bag, so you wouldn’t have to send it to your final destination, which was perfect for throw away ticketing (booking to a destination beyond the city you want to travel to, when flights to the connecting city are less expensive). Normally you can’t do this with checked bags, but a long enough connection was a workaround. Such long connections used to usually only be permitted on international itineraries, but are now allowed (and more common) on domestic award bookings.