Originally Posted by GogglesPisano

From the SRH:

"Do I have to accept the trip?
A pilot is considered to have accepted a pro er if he has verbally accepted the assignment from a schedul- er or acknowledged the rotation via IVR, the Crew Auto Noti cation System, or iCrew. When speaking to a scheduler, a pilot should ascertain whether or not the award or assignment is a pro er and, if unsure, should simply ask the scheduler.A pilot’s obligation to accept a trip on X days or regular line o days is not absolute, regardless of whether the trip is or is not a pro er. A variety of circumstances might prevent a pilot from accepting a trip.
For example:
• Not being physically located so as to be able to report.