I don't know if the 740 is the same, but I have always had trouble going back and forth between my home wifi and my Stratux wifi in the plane. The problem had to do with the 720 not being smart enough to realize a network was out of range, and still trying to connect to it instead of other known networks that *were* in range. I eventually decided the hassles outweighed the minor benefit of being able to use the 720 on my home wifi, and I deleted all the stored wifi networks except for Stratux.
I have not had any problems connecting my 720 to the Stratux since doing that. Since I use the iFly Connect software to update the 720's SD card on my Windows laptop, I don't really miss home wifi access from the 720.