In A Scandal in Belgravia, Sherlock cracks the code and John confirms it's flight 007. This triggers Sherlock's recollection of Mycroft saying something earlier in the episode on his phone, "bond..."? I understand how 007 is "Bond" but Mycroft says a few words after "Bond" which leads Sherlock to hypothesize about Coventry. What are those words? And what do they mean?
Mycroft just says "Bond Air is go," meaning that this flight with number 007 (or the whole secret operation with this flight full of already dead supposed terrorism victims) has permission to proceed/start. It isn't just that dialogue from Mycroft that leads Sherlock to realize the true nature of the situation, but the whole context of events.