There is always a sensible reason, even if it is not one you would choose yourself.
They are just as long as they need to be to get from one airport to another. Passenger kilometres are about the only way to make a meaningful comparison between different modes of passenger transport.
As the figures I posted show if I use my bus pass, I am generating far more CO2 than if I take a flight and it is quite difficult to get to somewhere like Madeira by bus.
I doubt there are many people who have been living in places that are under flight paths longer than the flight paths have been there. Why should they get preferential treatment over any other people who take advantage of the lower cost of housing that is blighted in some way?
Colin Bignell