HI
I'm a pilot, I've also written 2 unproduced feature length film screenplays.
I even have my WGA numbers if you need them. ;-)
I'll ask you a question. IF you were in your house and you were looking across the street at night, and your across the street neighbors house light went out, how would you know if the bulb burned out, or someone switched off the light switch?
Short answer is you wouldn't know. Even the next night, the bulb could have been replaced or the switch could have been used.
IN SHORT, there is NO WAY to know and all the talk on MH370 about the transponder being switched off is null and void until the plane is found.
WHEN the plane is found, you can look at the position of the switch and read if it was on, standby, or off.
So, in your teleplay, you would have to find the plane and find the transponder and look at the position of the switch.
How long? Well, they have to find it, get to it, move stuff around etc.
There are so many little things and no one in the NTSB would assume anything until the investigation had substantial evidence.
There are still cases , decades old, that people disagree on the cause or probable cause. Even though the NTSB has spoken on the subject.
It will be a hard script to write if you want to be faithful to the truth and have dramatic license in an hour script.
And one more thing. Even if the transponder was found switched ON, the antenna cable may have been disconnected, destroyed by a saboteur's acid, or half a dozen other things which would allow the transponder to be ON, but not received by radar on the ground.
Do you have any flying experience? Have you written anything that has been produced? Do you have an agent? Have you ever watched the movie, "FATE IS THE HUNTER" ( you can see it on youtube for nothing) and you will really get ideas about why planes crash at least in the movies!
Oh, do you like butter on your popcorn?
Sugar in your COFFEE? ;-)