There was a plot, but there was no way that there were going to be 10 planes blown up over the Atlantic at any time in August this way. A lot more developments would have had to take place for such a plot to even be practically conceivable.
The plot as it existed in August was blown out of proportion in the aftermath of the first arrests related to "the UK matter"; and the "security" reaction was overblown too.
Of course when 1200-2000 people have been monitored over the course of the year, it's not surprising that the above-referred "threat community" (located in the UK) finds a plot -- or strings together one -- and blows it out of proportion and/or jumps the gun for reasons independent of threat resolution.
For an example of this "stringing together":
Setting was early 1980s. A cabinet member sent a car to pick up a family member returning from foreign country "enemy#1". Next day the head of government calls in the member of the cabinet and says that they've received credible reports that General ____ from "enemy#1" is staying at the residence of the cabinet member. Cabinet member realizes there's been confusion but wants to see what the head of government knows and how good the intelligence is and so strings it along for a bit. Head of government says the report is credible and has been verified. The report says that General ___'s car dropped him off on the tarmac to board ___ flight and that the cabinet member's car picked him up on arrival and took the general to his home, where the general remained in hiding as of then. Cabinet member explains that the spouse's sister-in-law was picked up from that flight and the purported male general is neither a general nor a male; she is a doctor and a female. Lesson: intelligence doesn't always get all the facts straight before jumping to a conclusion.
