Chimbu - CAP above London, Paris, LA, NY, et al would be dirt cheap as the pilots, aircraft and support are already there. All you would be doing is moving the CAP a few hundred miles. Lets not forget that the UK up until the late 1980's kept a constant CAP plus a credible QRF and a short notice nuclear strike force.
Secure digital satcom could be provided for less than £2million per aircraft with frills. Beefed up doors would be less than £100k with cctv.
Or we could just issue flightcrew with .44 magnums and be done with it.
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