I was there and have sufficient medical that heat exhaustion was in play.
I grew up in the south and saw many people experience such conditions.
People of age both young and old are more susceptible to the conditions.
Try over an hour with no air.
The pilot and stewardess both knew the heat was at the least demanding and to some degree extreme.
Trained in biostatistics and wrote full hospital wide medical systems.
You would guess very wrong.
There needs to be more written guidelines than the arbitrary 3 hour rule.
In periods of heat, if no airconditioning, then cool water, ice or cold drinks are a MUST. Room temperature water is a
help but not just one small glass.
Otherwise, deplane.
Symptoms may not show for those on the plane until hours or days later.