Maybe after conducting a 'free' flight, you could stand at the exit door as the passengers are disembarking with your cap in hand ?
Might at least make something from the flight, even if its all small change
In the Company I work for it is common practice nowadays to be given heaps more responsibility or to cover a supervisory position for no extra pay or reward. The Company view it as a personal 'stretch' which "enhances your career development and propects".. I say Bollox.. its exploitation. I would never work for free, unless maybe I was making porn movies