I plan on booking a flight for friends using US Airways miles. It is:
PHL-ORD, Flight US1991
ORD-HKG, Flight CX0807.

The ticket would be booked together.

Since I will not be traveling with them, I want to make sure that the layover and airline switch is as seamless as possible for them.

1. Can they have luggage checked all the way through from PHL to HKG?
2. How is Cathay and US relationship? If say US1991 comes in late and close to the CX0807 departure, would you expect them to be "abandoned" since it's no longer US Air?

Thanks for your time!