It depends on what you mean by own metal. If another company is leasing that metal and paying all the expenses associated with that lease then they can and should control all the seats. Delta leases jets for charter all the time. As a Delta employee I can not ride at any priority on those flights. The aircraft are leased to a third party and they control all the seats. Lease a car from a dealership and let me know how you feel when they call you up and tell you that you have to carry passengers for the dealership when needed. After all the car is the dealers metal!!!