I have only had my PPL for a year and I have given up with anything more than simply replying "Yeah, I could take you up if you wanted".
I have only ever taken three people flying: My dad, ex-pilot, my boss, current pilot, a friend aspiring to be a pilot.
Seems that 99% of people would love to go flying, of which only 10% actually mean it, with only 1% actually turning up on the day without some crap excuse.
I think the reason is a combination of:
1. They don't think you are a real pilot because you don't have a uniform and you still go to work at an office.
2. They don't think its a real plane because it doesn't have 150 seats.
3. They don't think they will survive!
Their loss
