Planes bomb alert was more propaganda than plot
This, I believe, is the true story. None of the alleged terrorists had made a bomb. None had bought a plane ticket. Many did not even have passports which, given the efficiency of the UK Passport Agency, means they couldn’t be plane bombers for quite some time.
In the absence of bombs and airline tickets and, in many cases, passports, it would be difficult to convince a jury beyond reasonable doubt that these individuals intended to go through with suicide bombings, whatever rash stuff they may have bragged about in internet chat rooms.