Upvote:1
Some long haul aircraft are assigned to specific routes, but domestic aircraft are usually assigned as needed. Likely the only future "assignment" a domestic aircraft will get is a date with maintenance for a check up. And an airline the size of Delta has many 737s at its beck and call, so the chances of you flying the same aircraft on two consecutive flights is slim.
I fly lots of long haul and sometimes am on a connecting flight that carries the same flight number and is serviced by the same aircraft model, but different airplanes fly each leg.
Upvote:2
A few months out, any scheduling will be rough only, and thus even if you could get access to it, it would largely be meaningless.
However based on this being a 40 minute connection, you can pretty much guarantee that it will NOT be the same plane, simply because Delta (and most airlines) would not schedule such a short connection for the plane itself.
It takes time to get all of the passengers, baggage and cargo off the plane, and then to get all of the new passengers, baggage, cargo and food onto the new flight. This time is referred to as the "turnaround time" for the plane, and obviously varies based on the size of the aircraft involved, and the amount of baggage/cargo/etc.
Whilst airlines do try and keep "turn" times as low as possible, none of the major US carriers that do assigned seats will plan to schedule a 737-800 to turn in only 40 minutes - more normally it will be at least about 60 minutes.
(Note that's not to say that you won't find cases where it's 40 minutes or less, but these will almost always be due to rescheduling due to delayed flights, cancellations, etc).
So no, your 2 flights will not be on the same plane - however all of Delta's gates at LAX are in close proximity to each other, so the time to get between flights will be quick!