If they are public, no it is not illegal. If they are not public, but I have them because I provide a service to you, then yes it is illegal (most likely). In this case it is public information, and not even personal information. It is a plane identifier and that plane’s location. The only reason that tells you anything about it’s passenger is because said passenger is rich and entitled enough to own their own plane and use it for themself. It’s like buying the Empire State Building to live there by yourself and then complaining about someone tweeting out your address.