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...

I've seen the luggage storage place on the way out of the baggage claim areas, if I remember. Google suggests there are a couple options in some terminals. But I've not used them.

Ugh that's rough... perhaps ask @ JFK?

Ouch. I would send the storage bill to AS Customer Care, with a lovely screenshot of its web page, as there are no restrictions posted, such as sunrise, sunset, eclipse, anything turning into a pumpkin hour, moon hits your eye, and so on.

On second thought, I'd send the bill and complaint to an executive, as you're likely to get a response as meaningful as a canned reply to a PDB issue from Customer Care.

I've got a similar case coming up in SFO traveling BWI-SFO-OGG. Arrival at SFO is 9:50pm departure is 7:40am.
We are okay within the 12 hours.
However, do you think the bag will be stored in a safe place not at risk of pilferage and they will remember to load it the next morning?

I'm wondering if Alaska may pull out the "they are booked in two different PNR" cards and say no to any compensation. Some airlines aren't even allowing agents to add in other airline segments or connections - everything has to be booked at the same time from the same source!

There also could be an issue in JFK because of the overnight "storage" of bags. TSA sometimes won't allow it depending on the circumstances - and being a large international airport, it very well could be a local TSA rule...

let us know how this turns out!

Well, the agents tried, so they believed it to be permissible, but the system inhibited it for a reason - and perhaps there's a legitimate reason, but the passenger needs to know about this prior to travel (which includes prior to getting to the airport).

Yeah, this is why I'd be extremely wary. Last year, after my bag missed a tight connection, AA kept it at MIA overnight to load it on the following night's SCL departure. Someone that next morning threw it on the CCS flight instead, and I wound up getting my luggage a whole two days late. The longer your bag's sitting around, the greater the likelihood something is going to go wrong.

The point where carriers hand off bags to each other seem the be the most common point for lost/delayed bags. Back when i checked bags, i always short checked on overnight layover even when its the same ticket.

The policy is clear that they will check through/interline a bag if the layover/connection is 12 hours or less; it isn't clear if they will do this if one is traveling on separate tickets, which the OP stated s/he was traveling on, as the policy states, "...on your ticket," not "...on your tickets."

I booked a business class reward ticket the other day to Australia with the outbound being RDU-SFO-MEL and the inbound just MEL to SFO as Qantas wouldn't allow the routing back to RDU, despite there being inventory on AS from SFO to RDU (this was according to the agent I spoke with after I could not book MEL-SFO-RDU together online). Therefore, I had to buy a second ticket from SFO to RDU (though honestly, I was fine with this because I GOT A BUSINESS CLASS REWARD TICKET ON QANTAS!!!!). Both tickets are on AS stock (while the OP's tix were on AS and JL). I was told that my bag will be checked through to MEL on the outbound despite the long layover of 11h25m at SFO, though it would "would be wise to pack essentials in a carry-on," while on the return I would have to ask at check-in if Qantas would tag my bag all the way through to RDU. The agent told me that they *should* do it since the two are partners, despite it being two separate tickets, and because both tickets were on AS stock, but she made it clear that I would be at the whim of Qantas. I have enough time to clear immigration at SFO, get my bag, and re-check it with Alaska (3 hour layover), but I would of course just prefer it be interlined. But, as was clear from my conversation with the agent, if traveling on two tickets with AS and a partner, the interline agreement is perhaps NOT guaranteed, even if both are on AS stock.

If it's not allowed, that's fine, but the policy needs to be clear in the website. I would have packed differently had I known.

In my situation, I am not getting a hotel for the overnight It's pointless -- with 3 hr jetlag I would not get any sleep anyway. I just landed in JFK; I'm going to grab a lyft to manhattan and go out all night, and be back at the airport in plenty of time for my 7am flight. Having a bag in tow is not what I'm looking for.

It is clear. As noted earlier, it say ticket (singular). You had tickets (plural), which is outside the policy being referenced.

They are very wishy washy when it comes to checking bags through on separate tickets. I often book PDX-SEA-XXX on 2 separate reservations. Regardless of the layover time, they won't guarantee that the bags will be checked through and they say that I have to check with the agent at PDX during check-in .

My recent flight PSC-SEA on AS, then SEA-ZAG on Lufthansa, separate tickets, they booked my bag all the way. I was pleasantly surprised, saved me having to get the bag in SEA, wait around a couple hours before checking in.