Lots of fantasy in this thread . the title is also misleading . Interception training is done using other military aircraft or special flights. ( Germany for instance uses a small specialized company using Learjets) No need to intercept civil airliners in civil controlled airspace .
Intercepting Concorde a M2.0 at FL600 ? Good luck with that one .
Most interception of civil airliners (over 90% in Western Europe I would guess) are due to loss of comms, and most of these are just finger trouble, wrong digit tuned or forgot the google switch. Expensive mistakes specially since some States are reported to send the bill to the airlines .involved. But verifying /intercepting radio failures is a standard normal routine procedure in many places right now, Get used to it.