Just a datapoint... I had a 9 hr overnight connection in JFK on separate tickets. The agents tried to check it through to my final destination, and had all the segments up (4 total) but the JFK connection was showing up as an illegal connection. It was AS -> AS metal; AS -> JL ticket stock. Two agents couldn't make it work, one went to talk to a supervisor and came back saying that the other is that they won't store the bags in JFK overnight.

This is not what the website claims -- just a warning.

Does anyone know if you can rent lockers or something anywhere in JFK? Something big enough to fit a carry-on-sized bag and preferably a backpack as well...