So I found a glitch were if you have Simpleplanes on 1 device and import it on another you have on both however if your using a different Google account on the import device it will say you have too buy it but all you have to do is just turn of WIFI and mobile data and it loads and you can play it.
Please be a good person and don't exploit this. This was on Android I dont about Apple or other brands

Developer's I hope you see this and fix it