Nothing is off the table until they find wreckage, right?
Let's go all the way out on the edge... aliens is
off the edge, so this is about as far as you can go and still be a terrestrial theory...
Check out these two conspiracy theories on Veterans Today... and
do not hesitate to read the comments sections, as they are just as scary/fun:
NEO – Flight 370: Another US Conspiracy? | Veterans Today
FLT 370 – A Little Bit of Prestidigitation | Veterans Today