I had a similar experience using an AR1000E receiver binded to my DX6i.
I cannot determine the exact height and distance of my plane but to compare a 1200mm plane as big as my palm up in the air must be less than 200ft.
I lost response from the plane at about 4minutes into flight and fortunately the plane glided down and broke only the propeller on impact.
I was told that the AR1000E has an indicator of a brownout, when the led turns flashing during flight means that the Rx has experienced a brownout .
Hope my experience helps.