Not only that, but this also raises the serious issue that, as a Doctor, you are morally obliged to assist a passenger in distress.
Although medicine is your chosen profession, you receive no payment for your professional act. You would never refuse treatment to someone just because you're not being paid for it...but suppose there's a complication a few days later? Are you liable?
There was an article in the papers about this a couple of years ago.......possibly James leFanu in the Telegraph, but don't quote me on that.
Whatever the outcome, you are to be praised for volunteering your services, and making the best of a poor situation.
It's a real conundrum, and I've no idea of a way round it.