Range

I believe I included the recommendation to range check before you fly.  Most if not all RTF packages have a range check procedure.  But also check the recommended maximum range.

You may see RC guys flying planes high and far away and figure you can do that too, but maybe not.  Many RTFs come with limited range radio systems.  This does not make them bad as the radio is likely suitable to this plane. 

However, sometimes people pull the electronics from a crashed RTF and try to use the included radio/receiver combo to fly another plane and don't realize that it is a limited range radio/receiver. 

RTFM, read the friendly manual and the box and all the documentation that comes with your RTF.  There should be a range limit statement.