I thought it had some strengths as a drama, just wasn't anything that should have been a Sherlock series. It completely missed the whole idea that following psychopaths is a bad idea, and John/Sherlock and even Mycroft would have most likely used the gun to shoot up the place and ensure the governor survived.
And the girl on the plane looked like a dream/vision from the start, with all the people being so neatly asleep.
Basically Moffat is clearly really really annoyed he didn't get asked to write any of the Marvel superhero films...