There were discussions about the 1h25min connection between AY15 and (aa-operated) AY4172.

I tried it on Sunday and the results are inconclusive: the plane landed early at 18:56 but then there was 30 minutes of taxiing and 30+ minutes of waiting for a gate. Cabin doors opened at 20:18. Apparently a QF flight needed to return to gate to unload a passenger with medical emergency.

There was an agent with red envelopes waiting at the end of the gangway. My boarding pass had already been taken out of a red envelope as the agent felt I would certainly miss my connection, which was supposed leave at 20:35. It was delayed by about 10 min but the agent was correct: not a snowball's chance in HEL in July.

For some reason the CBP agent didn't see my MPC form so I had to go to a regular lane. The app said everything was fine.

While waiting for baggage to arrive I got an email telling me I had been booked on DL315 departing 21:40. I was at the check in desk with my bag a little after the 1 hour cutoff DL has in JFK but the agent was able to late check my bag. Bag arrived on the same plane, although this isn't guaranteed.

Also, for some reason the agent couldn't add my SK gold number to my ticket. Said it was invalid. Maybe I should have added the EBG on front of it? Or maybe the systems integration isn't done yet.

I did get to prio security by showing my digital card. I would not have made it in time through the regular queue.

I even managed to get a burger from Shake Shack and eat it while waiting for boarding group Ö to be called.

DL315 was delayed a bit ended up in SF about 2.5 hours after planned. To quote a meme: "Never stop the madness ja kohta vedetään taas".
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tl;dr 1h25min layover in JFK might be possible if everything goes well. AY sometimes books you on non-OW carriers in North America to get you to your destination on the same day.