[albert_e]

that's a great idea -- though i have not experienced this myself (except in some movie theaters)

I presume such chairs are costlier to manufature and maintain -- so most cheap airlines do not opt for them

[bombcar]

More likely they're a newer design, and won't appear in the cheaper airlines until those planes trickle down.

They're singled in the middle so the bottom slides forward, the top slides back.