I for one think it stinks.
Those of us who are employed by operators with night stops-ex UK /longhaul trips genuinely spend a portion of our pay Duty/FDA/Flight Pay/ Allowances whatever abroad making no contribution to the UK economy in that sense!
They simply do not have the Right to Tax that money...for my particular circumstances. End of story.
What I fear is that they will apply a blunt policy designed around examples in carriers where no ex-UK stops are involved and therefore deem all income taxable as it is intra-UK.