I've realised why my laptop keeps going into Flight Mode, in the F keys, F12 is Flight Mode!! When I'm trying to type in the dark - well not exactly dark but using the light from the next room I sometimes hit the wrong keys, especially if I'm trying to use +/=. Unfortunately, although it's so easy to do, to take it out of Flight Mode, I have to go into Settings.
greenrig - Laptop doesn't freeze or shut-down just when I use WiFi, it does it when I'm using the router wirelessly. I don't think it's the laptop, more the way the router is connected. Our grandson who works for Openreach tried to fix it, he knew the problem was in a cable under the road but, obviously couldn't start fixing that without permission and it took another 2-3 visits from different Openreach engineers before one found out the problem was exactly as our grandson had said. The outside cable was fixed but now we think it's probably the router, as the same thing (not the flight mode) happens to my husband's tablet which is only inches from the router. So one day my laptop will be fine and his tablet is playing up, another day it will be my laptop playing up and his tablet is fine.
We are just waiting for Virgin to lay cables down our road, they've done the majority of our town, then we'll probably switch to them. I know some people don't like the company, but we used to have them at a previous address and never had any problems. My daughter is on Virgin cable too and in 15+ years has never had a problem.