Unfortunately, there is no chance that you can use RWT to generate the whole world.

In your case you need to use something like Online Maps.
OneWorldSDK works the same way as Online Maps, but not as RWT.

Is there ah way can use whole world earth
Noz need be round

With worldstreamer or world streamer 2

You add also world stream 2 support or better use it manually

Like this for example but with RWT
https://github.com/SimBlocks/OneWorldSDKforUnity

And is there a way that create whole earth with RWT and wolrd stream 2 but that can add more countries or continents then because whole earth with RWT in 1 screne will be do big. Before create multiple scenes with World Streamer 2.

Or can combine   this https://github.com/SimBlocks/OneWorldSDKforUnity with RWT for Buildings River and more.

Both will be good find a good solution for flight simulator game with whole world earth.  But with RWT and WS2 near if get out of plane have also good looking game.

Regards