I have my first electric plane and have a battery with Deans connectors pluged into the speed controller. Everything works as it should, but now that I am ready to actually fly it, I realized that after I power up my transmitter I have to plug my battery into the speed controller. Am I supposed to use a switch harness like I do on my glow airplanes or what? I am afraid I will drain the battery if I keep it pluged into the speed controller, then again, I don't know. Is it just best to leave access to the wires in the bottom of the plane for easy connect/disconnect?

Most of my electric planes have no switch. I turn on my transmitter, then I connect the battery in the plane, then I fly. When the flight is over, I unplug the battery from the airplane and then I turn off the transmitter, in that order.
You are absolutely correct, you do NOT want to leave the battery connected to the plane. It doesn't matter what kind of radio you are using, you ALWAYS want to have the transmitter on before, during and after the plane battery is connected, because some stray signal could start the motor and launch your plane across the garage, the field, or into your face.
If you do have a switch harness on the plane, you STILL want to disconnect the battery when not using the plane, because your receiver will slowly drain your battery down to nothing, and if that happens to a LiPo battery, it WILL be trash.

Thanks, that's what I was thinking. I'll just leave access on the bottom of the plane to connect and disconnect the battery.