What does the term "per diem" refer to in the context of airline crews?

In the context of airline crews, "per diem" specifically refers to the daily allowance provided to crew members for food and other incidental expenses incurred while they are away from their home base. This daily compensation helps cover the costs of meals and any other necessary expenditures when crews are on duty in airports or cities away from home. It is an important aspect of crew compensation, ensuring that they are supported during layovers or extended trips.

The other options pertain to different aspects of airline operations or crew remuneration but do not accurately define "per diem". While the hourly wage for flight attendants is a crucial component of their overall pay structure, it is distinctly separate from the per diem allowance. Revenue generated per passenger refers to the financial performance metrics of the airline, and bonuses for on-time departures relate to incentive programs, but neither of these concepts aligns with the definition of per diem for airline crews.