Some things are not easily kept secret, such as airplanes, which require fuel supplies, advanced repair facilities, and more logistical support for the pilots, so airports are generally built in places that are not too remote.
Even for the sake of secrecy, some airports might be located far from urban areas, but an airplane's flight has altitude.
Even tens of kilometers away from the city, if a plane climbs to a few thousand meters in the sky, it might still be seen by people.
However, some things are much easier to keep secret than airplanes. One such thing is another secret weapon from Great Tang Group—tanks!
In fact, after the automobile was developed, the technical difficulty of producing tanks no longer existed.
The technological gap between it and armored vehicles was really just the brainstorm of a track system.
But Tang Mo didn't need time to accumulate; the idea of the track system was already in his mind.