North West
Come on, I am aware that there are lies, darned lies, and statistics and your figures just about prove the point.
A very large percentage of BA domestic passengers from airports further north than Manchester are travelling point to point. However, anyone wanting to travel to London from Manchester on business would need their heads looking at to fly to Heathrow - unless their business was on the Heathrow side of London. On such short journeys the hassle of flying makes rail the obvious answer for the business passenger.
And why restrict your stats to the middle eastern carriers, a large percentage of Lufthansa, Air France, KLM, Swiss and Turkish passengers flying to and from Birmingham are not terminating at the FRA, CDG, AMS etc - but transiting.
The difference with Lufthansa, is that even through their newly metamorphasised group member, they will offer decent European business services from most major Germany airports - BA offer nothing, zilch, diddly squat. They have little interest in the UK outside of London.
In my opinion, that's not good for UK Plc, though of course the bean counters in BA may feel it's better for their shareholders!