Flying pay is a retention bonus for aircrew that have an obvious skill that could be transferred to civvie street. whether it is flying a "model" or not it is still a skill that for example a clerk doesnt have.
Would you expect an SF soldier to lose his SF pay if he was doing a job in MoD rather than jumping through embassy windows? or a submariner to ose his submarine pay if he was doing a training job on dry land?
Its the same thing
HG