Twice, I have gone out flying, and after a few minutes, I noticed the back of my control unit felt funny.. When I turned it over, I found the battery cover was gone.. I don't know if they have a weak latch, but I usually lay my control units on the bed, in between flights.. Both times, this is where I found the cover.. I'm tempted to maybe add some duct tape or something on the cover, just as a safety precaution.. Seems to me I read somewhere about dire consequences, if the batteries fall out..