Leaving the money side out of it and the obvious profit motive over community need I find distasteful, Plymouth does need more housing, not more airplanes. There's little demand for it, although the Cork thing was handy once upon a time.
I don't fly regularly at all, and believe, as in life, it's the journey that counts, not the destination. If one spends too much time travelling for work, may I humbly suggest moving closer to one's workplace... radical, I know.
As for the London Peter Jonesesque 'the city needs it' routine... no it doesn't, but the second home owners certainly would appreciate it... and the more highly subsidised it is, the better they'll like it.