I'm no legal expert, but I know of at least 2 private jets, operated by different companies (neither of which are RYR or anything to do with them), and based in the UK, which are routinely used to ferry spare parts and engineers around the UK / Europe, on behalf of UK-based UK-AOCed airlines (1 airline per jet, not just any airline).
In one case, the person who owns the jet also owns the airline. I'm not sure about the second case.
The jets are not on any AOC. Several of the pilots even only have a CPL and no ATPL. It's been going on for more than 5 years with one aircraft, not sure about the other.
My "rule of thumb" with this sort of thing is, if the wording of the relevant regulations is ambiguous, always look at what the other people are getting away with, because, if nothing else, when you get nicked you can point and say "but they're doing it too".
