Would JAL do same day changes using miles
 

JAL have 2 flights a day from HND to NYC leaving at 11:05am and the other 6:30pm.
Managed to get a business class flight on the 6:30pm flight using miles but i really want the 11:05am flight.
On the day of the flight can I turn up early and ask if I can get the earlier flight or the day before I can take a quick trip to the airport and ask customer service.
Anyone know if it would JAL would change a flight if booked with miles and if business class is available?

On the assumption that, if business class really was available on miles you would have booked it or changed your existing booking onto that flight, then no; you cannot just show up on the day and expect to be carried on the earlier flight for free.

JL won't touch the AS ticket. They'll simply tell you to contact AS to see if the flight can be changed.

I see someone wants the new JL J product?

Anyway, this isn’t like the US where everyone does same day changes at the drop of a hat. You’d need to contact AS and rebook the award for the different flight, assuming award availability is there.

They will if it serves their interest; i.e. oversold. I've experienced exactly that on JAL.

Hoping for an oversell is kind of like hoping for a winning lotto ticket, isn't it?