If only! Even the Department for Transport says that airport Master Plans tend to be so over-optimistic about future passenger numbers that it applies its own “pinch of salt” discount when it produces its national forecasts.
For example: in 1991 Manchester Airport wanted to build a second runway, and promised this would create 50,000 direct, indirect and induced jobs.
The runway opened in 2001, and by 2006 there were 4,000 additional jobs at the airport. Even allowing for another 2,000 indirect and induced jobs, the promise of 50,000 extra jobs was just a flight of fancy.