Hi All--The Canadian regs say there must be one FA for every 40 PASSENGERS (not seats) and this has me wondering...

Example: 175-seat aircraft. 85 passengers booked. How does the airline staff the aircraft and what about last-minute walkup passengers? If you have 3 FAs for the 85 people what if a flight cancels or for whatever reason the plane fills up? Where do we get the other 2 FAs?

Would this be a reserve call-out situation? Canadian carriers must make good use of "Airport Reserve" for FAs?

Or might an airline have to turn passengers away because they do not have the right number of FAs for a given pax load? Would they leave pax behind if they couldn't get the additional crew members?

Thanks in advance for any help on this. For some reason I've really been wondering how this works lately.