Airfields,like Shipyards but for planes. Allows to use planes around the area,maybe a 1,000 block Radius. Airfields can be inside towns unlike Zeppelins and Aircraft Carriers. You can somehow toggle them as piloted so you dont need several people to fly a damn plane. It's one thing that can make planes more usable while not making them fully indepedent of all boundaries but also not make Aircraft Carriers obsolete.
Planes rarely get used because they require support movecraft like Zeppelins which are rather feeble or Aircraft Carriers,which are on the sea and rather feeble to other naval movecraft. On top of that they require other pilots which is something rather unfeasible most of the time. Considering how planes are only good in land battles,I dont see why they shouldnt have a 1 person pilotable option for land operations,via airfields.