The incoming cultivators weren't flying, but judging by their speed, Rean was certain they were already Zone Gods. We couldn't forget that flying in both the Zone God and even the Law God Realm was extremely taxing, so most cultivators would rather move through the ground whenever possible. Unless there was some specific reason to fly, walking or using other methods of transportation was simply more efficient.
One thing that must be mentioned was the fact that this City Prison of Woster didn't seem to be particularly well-developed. Even after all these years, the twins' group and the others hadn't seen a single airplane passing by the Ashen Hills. Considering how common airplanes were in Besgol, the difference was quite striking.
