Many good points and explanations here blaming the reciever battery. I guess it was just coincidence that my crash happened as a real plane passed over.The fact is that my rx battery was low (not extremely low) but low enough to cause some problems. After hearing everyones input, i think its safe to say it was the battery and not he full scale. BTW thanks guys for the replies .......
In the future, i'm going to buy 2 or 3 spare batteries and and swap them every 3-4 flights. It's easy enough to switch batts and certainly affordable.
Jamie