Thanks for that.
So with US and UA I get 100% of the miles even if my flight is with a different carrier? Or is it just if I actually fly with US or UA?
What would the benefits of getting one (US or UA) over the other be?
Also, so there's no penalties if you book flights with carriers other than the one you have FF with? So if I was going to Thailand (hypothetically), would there be any disadvantages to having FF with UA or US instead of Thai?