Originally Posted by
2Donkeys
Unfortunately, as with all things legalese, Common Purpose doesn't quite mean what you are attempting to make it mean.
Common purpose does not mean that both parties to a flight are both going to the same place for the same reason. It simply means that both parties would be going to the destination for their own reasons - their purposes are aligned. In other words, in the context of pilots and flying, the pilot needs to have been going to go to the destination in any case - and is not merely flying there for the purposes of conveying the passenger. Pretty much exactly what Yodice wrote.
I can't find the link now but it was referenced in the Cardiff thread. In that link, which I think represented an FAA opinion, it was stated that, if a pilot flew from A to B with a passenger, then the pilot had breakfast at B but the passenger attended a business meeting at B, then the flight was not a legitimate cost sharing flight because the pilot and passenger did not have the same reason for making the flight. Perhaps someone with a better memory than me can point us to that reference.