I think what the poster above said is the likely outcome. But there might be a way around this.

Is there a flight from JFK to your final destination on the same day that you arrive? If so, you may be able to request to be put on standby for that flight at the counter. They should then issue you a standby gate pass, which would let you get through TSA and then go to the lounge. YMMV.

Just was wondering any changes to FL access not being allowed on FJ J flight? I know upthread a year ago it was a NO. Was thinking of entering at T4 to avoid the Bradley Zoo at night, grab a glass of champagne and then walk to Bradley.

Depart MIA in PE (no upgrade to J). Arrive LAX. Depart LAX in F transcon. Access to Flagship Dining in MIA possible?

edit: same day departure from LAX

So you are flying MIA-LAX-JFK/BOS? Why?!

If you have a boarding pass showing a same day departure in transcon F from LAX, they should let you in.

Assuming OP is on the 9am departure ex-MIA, this would get him into LAX at 11:30am. If he's taking a redeye to JFK/BOS, this means he will have almost 9 hours in Los Angeles for meetings, etc.
Alternatively, he could just be like many of us on FT who have an irrational love of flying.

Its the latter! 5:13 pm out of MIA then 11pm out LAX to JFK...plus a few more connecting flights after that to get home. Why take one or two flights when i can take 6!

My lounge questions will have to wait. I didn't get upgrades at window and don't want to fly that far without Flag Lounge and a lie flat guarantee...Canceled all of it and booked the more direct MIA-CLT- GRR (vs MIA-LAX-JFK-ORD-AZO). For new route, $289 with almost instant upgrades on both legs...its cool.

Flying BOS-LAX in flagship first, then connecting to LAX-HNL in "business J" (regular domestic first class on A321neo). Will I have access to both the Flagship First lounge as well as Flagship First Dining at LAX by virtue of my arriving flight? Less importantly, will I have access to the Admirals/Sakura lounge at HNL on arrival?

You will have access at the LAX FL due to the inbound (FFD is not open). You should also have access at the BOS AC due to the F ticket.

Assuming there are no nuances with the HNL AC (i.e., standard AC rules apply), you should have access via membership. I’m not certain with the ticket, but check the AC access page and it should confirm it for you!

Flagship First Dining is never coming back at LAX. AA has abandoned LAX.

This has been confirmed by AA or is it just a feeling from how they're operating the AA lounge?

This is from speaking with staff, they don't think it's coming back.

Add to that;
a) AA has dropped several international routes from LAX over the last 3 years, and
b) AA is getting rid of First Class.

Took a bit of explaining at MIA today that a F transcon flight later in the day JFK-SFO also means access to dining in MIA. The more experienced, friendly agent sorted it out.

Even worse than my LAX FL denial on LAX-SFO-JFK w/ SFO-JFK in FF was what happened at Miami last year. Agent last name Gonzalez is so incompetent (like the LAX agents were who said LAX-SFO isnt a Flagship route and were trying to justify that it wasnt listed online as a qualifying route......like why would it be, how can AA list every possible connection to a qualifying flight). But this Gonzalez lady at MIA then took it a step further after finally letting me in (LAX-JFK-MIA-BOG) and denied me FFD b/c I already used it to at JFK. I had mentioned earlier before I realized she was so horrible that I was excited to compare FFD's. Denied FFD on some BS rule that only 1 FFD location is allowed. Just thinking about this again makes me so mad.