Thanks for the info, can you post a link to the Master Agreement? Did a quick search but didn't come up with it.
(7) Air drivers may, on an exception basis, be used to make service
on packages which are not air packages.
An exception package is intended to be when an Air Driver is making
a pick up, as outlined above, after the regular driver has been at the
customer’s premises, and the customer has an exception ground pack-
age(s) for shipment, the air driver may make service on this pack-
age(s). Air drivers may continue to pick up Automatic Return Service
packages but the features of this service will not be expanded.
Any violation of Section 1(a) (7), shall obligate the Employer to pay
the Air Driver involved the difference between his/her rate of pay
and the top regular package car driver wage rate existing at that
building. Grievances concerning violation or abuse of this shall be
referred directly to the National Air Committee.