I had the joy of attending a meeting in Abbey Wood last week. In one of the tree house cafes, there was a Sqn Ldr aircrew type in DPM rig and special non reflective boots. Perhaps the airlines are saving us from
JS uniforms regs. That said; doesn't explain the requirement for plain clothes on the Timmy down to MPA.
A serious point: many years ago, wasn't there a hijack of an A/C with uniformed US serviceman on board? I seem to remember that they were singled out for special treatment.