Not an aviation expert or enthusiast, but I'd imagine in a commercial airliner if the gear was not deployed and the pilot was trying to land, at a certain point the plane would start yelling at the crew something like "NO GEAR" "NO GEAR" "NO GEAR (deployed)"
So I don't think a pilot can just "forget" to deploy the landing gear in a commercial airliner.
This does not only happen to little propeller airplanes. Heres an Airbus A320 where the pilot managed to land gear up despite the presence of all kinds of safeguards and automation.
I think the 777 landing gear warning is based on flap position, eg flaps 0 you won't get a warning, but you will probably get a GPWS configuration warning instead!
> I think the 777 landing gear warning is based on flap position
It isn't. If you're within a thousand feet of terrain, a runway is nearby, and you're at an approach for landing speed, it blares "TOO LOW, GEAR" in the cockpit over and over again. If you're going faster than approach for landing speed or there is no runway, it instead blares "TOO LOW, TERRAIN".
Likewise if you deploy more than flaps 20 without the gear extended (regardless of your height above terrain or the presence of any runway), you get a master warning and "CONFIG GEAR" in red on the EICAS.
So I don't think a pilot can just "forget" to deploy the landing gear in a commercial airliner.