Here's the part the cushion aisle never explains.
When you sit on a flat seat, your whole body — all of you — comes down on a patch of bone about the size of a credit card.
Your tailbone and two sit bones, holding up everything, for hours.
That's the real enemy. It even has a name: the Pressure Pooling.
And it doesn't stay still, it builds.
Every hour, more of your weight digs into that one spot.
Blood gets squeezed out.
The nerve gets pressed flat.
That's the numbness. That's the burn. That's the ache that creeps into your lower back.
It's why you're fine at takeoff and unbearable by hour two.
Padding can't stop it. It just softens the hit for a while then packs down, and you're right back on the bone.
There's nowhere for the pressure to go.