how do you know if you have a VX plane?
 

Might be a dumb question but I'm looking at booking a flight out of Philadelphia and I have not flown VX since the merger. Is there a chance I might be an Alaska Airlines plane? Is there a way to tell?

Because it will be a VX plane sold as a VX flight. They aren't merging anything meaningful to passengers until next year. Even if you book a VX flight on Alaska's website, it will state clearly that it's a VX flight (and vice-versa).

If you are on an Airbus, you are on a VX plane. If you are not on an Airbus, you are on an Alaska (or regional carrier) plane.

If it is PHL-LAX/SFO its VX.
In the coming weeks all VX flights, AS codeshare or VX marketed will be numbered 1XXX.