I'd like to add on to this. I had the same idea today but I'd like to make it more specific: Instead of Base-specific marketing I suggest adding Airport- or City-specific marketing. For example, The airline I'm currently running has 4 bases. If I intend to expand into a new market from all 4 bases I would need to have 4 separate route-specific campaigns. My suggestion would be to make it airport-specific so one campaign would effect all 4 routes in my example. Of course, said campaign would need to cost more for each route it wouldeffect. City-specific would also work where there are multiple airports in the same city (New York i.e. JFK/LGA comes to mind) and one "local" City advertising campaign would effect all of an airline's routes going into an airport in that city.