Originally Posted by
ausgambler
There is an earlier flight (4 hours earlier) that seems to have availability (20+ seats on the seatmap, though most are in Y+).
UA does not have Premium Economy on LAS-LAX. Economy Plus seats are considered part of Economy, which is good for you because it means they count for the purposes of standing by.
Originally Posted by
ausgambler
Getting stuck in LA would be of no benefit to anyone; I'd assume they'd have to pay for overnight.
I would not assume that.
The 4:35 PM departure is currently X5, meaning you might be able to confirm the change now via Aeroplan. Otherwise, what's going to happen tomorrow is anyone's guess: technically you're allowed to standby with checked luggage, but many agents refuse to follow the policy. If you explain why you're at the airport five hours before your flight, you may get a sympathetic agent, or you might not.