Why should it change? It's just like home WiFi where the plane has one in-house router and getting data from one satellite.
Re IP location, most IP locators have me living about 3 states away (Australia) which is the registered business address of my ISP. Before that I was using a local ISP whose netblock was owned by another ISP in the next state but most European ISPs had that network blocked believing it to be located in Taiwan.
IP is most unreliable because blocks within blocks can be used in other countries. It can also be spoofed.