Dudley Henriques writes:

If what he says has merit (God help us :-) that big ole 747 up there
with all 4 shut down should actually be able to CLIMB in those l'll ole'
thermals right over there now shouldn't it

I have pondered that exact question. But the simulation of thermals in MSFS
is not entirely realistic. I rather doubt that anyone has tried it, in
simulation or in real life, but that doesn't mean that it cannot be done.