@Dioxine
Actually that was the impression I got, that there is a huge huge shaft above each Hangar which the aircraft lifts off through.
This is why all of the Xcom aircraft have VTOL. Skyrangers and Interceptors do not take off and land like normal planes even if they can. And all of the hybrid craft can do it implicitly.
Also notice that when you send an aircraft off on an interception mission, there is a few minutes where the plane just sits there hovering over the base before it starts moving. Determined primarily by its "Acceleration" stat I think. If the plane had to vertical takeoff its way up a 300-600 meter shaft that would take a few minutes I think.
...what? What have you been taking, man? I want that too... Crafts accelerating up a quarter-mile shaft, barely larger than their wing-span... Hell, even thrice as wide, makes little difference... See what's the problem here...? KA-BOOOM!
...not to even mention that such a huge shaft is far more than a guided bomb needs, the US airforce managed to incinerate many (mostly civilian) bomb shelters throwing a guided bomb from a plane down *elevator* shafts, few metres across.
Oh yeah and excavating such a shaft would take many months to even years, depending on (hugeness of) machinery used. Just sayan.
Yeah except these three little things your logic is sound.