Indirect employment is just a way of double-counting people who are already employed in other industries. If every industry counted its indirect employment the way airports do, the number of people employed in British industry would far exceed the total UK population!
For example, indirect employment for airports includes workers who produce the goods sold in airport shops, for example, the Scottish distillery workers who produce the whisky sold in duty-free shops. It includes the bakers who bake the bread for the airline pilots’ sandwiches. It even includes the bakers who bake the bread for the distillery workers’ sandwiches!
It includes the workers on oil rigs producing fuel for aviation. When an oil rig worker takes a holiday in Cornwall, a proportion of the hotel staff are counted as part of indirect employment for airports. Honest.
Even if you believe in this fantasy of indirect jobs, far fewer are created than airports would have you believe.
Consultants for the Department for Transport looked at the number of local indirect jobs that aviation lobbyists claim have been created for each direct airport job. The average was 0.3 indirect jobs created for each proper direct job. Stansted itself quotes this number for its own indirect employment creation. Bizarrely, Infratil says that it will create 0.5 indirect jobs for every direct job.