JFK Terminal 4 to Terminal 8 Transfer Doable in 30 minutes?
 

I've seen some threads about this on Google, but most are Terminal 8 to Terminal 4 with checked baggage etc. I will be flying in from LAX to JFK Terminal 4 (Delta One, no checked bags) at 7 am. Given that I should be deplaning first, would it be possible to make it to Terminal 8 for a separate ticket American Airlines flight to BOS departing at 7:57 am? My inclination is that it would be tight but doable since I have no checked luggage and will not need to go back through security or check-in (will be on mobile).

You will need to go through security at T8 as the airtrain is landside. If theres any delay you are SOL, I would not recommend this.
Also, its appropriate to add that DL's JFK T4 concourse is insanely long. If your plane parks at a gate towards the end, it could take a while to walk towards the terminal exit.

Ah, slipped my mind that AirTrain was landside. Thanks, will not do this then!

Book a later flight and do standby on the earlier?

OP may have a compelling reason for wanting to take AA, but I'm pretty sure DL has at least one early morning JFK-BOS flight that they sell as a legal connection from the redeyes ...

TCONs from LAX typically park within a couple of gates of the SkyClub (and widebodies can't use the high B gates at the far end). When they don't the usually arrive in T2.

That said, it's still a solid 10 minute walk to the AirTrain, then another 10 minutes to change terminals (if the AirTrain is running normally), then clearing security. Theoretically doable, but I wouldn't try it.

If everything goes exactly as planned, flight being early would be nice, then it’s possible. But anything goes wrong even slightly, then no.

Violating MCT on a split-ticket connection is always a terrible idea. Full stop.

I think it's totally doable if you hustle, and if the flight is on time, and if the DL flight doesn't arrive at a high-40s B gate (that's a ~12 minute walk to curbside maybe 15m to AirTrain), and if the AA flight doesn't depart from the far end of the remote concourse, and if the AirTrain is running properly, and if the AAgents don't decide to close the door 10 minutes early in their relentless pursuit of "D0" ontime departures.

It's a lot of ifs. My best guess is that you'd make the flight 65% of the time (admittedly without checking the track record of the inbound DL redeye). So what's your risk tolerance and the potential cost of that other 35%?

Perhaps OP is trying to save money, but connecting in JFK doesn't make a whole lot of sense when the logical routing would just be the LAX-BOS nonstop.. it's a D1 route too.

JFK is a perfectly logical routing . Nonstop is either 8am or 10pm. Doesn't always work for everyone.

In this case OP is already flying the redeye from LAX. The only difference is that LAX-BOS redeye leaves an hour earlier than LAX-JFK. Not sure if it's worth a connection to change your departure time by an hour.

My guess is 43% assuming that the OP gets PreCheck for the flight.

otoh, not sure if OP has the ability to reschedule whatever is on the calendar that day in LA to be able to make a nonstop that departs an hour earlier ...

While MCT does not apply because this is not a connection, the fact that carriers will not sell this as a connection tells you that they do not want the risk of a misconnect.

AA requires passengers at the departure gate no later than T-15. While AA will not generally offload a pax until the flight is closed, it will do so if it needs the seat or if the aircraft is ready to go and all passengers at the gate have boarded. Thus, this gives OP 15 minutes to make it from brakes locked on the inbound to the gate reader on the outbound. That seems unlikely and the risk means that he purchases a new ticket to BOS.

Agree with others that unless schedule and other factors do not work, flying this as LAX-BOS may make a lot more sense. I would, in any event, price the ticket with the change. It might not be far off.