[imglorp]

Not hard and the glider needn't be special; most already have a stunning glide ratio. I've been up in lesser wave in a clunky old trainer. You do need to coordinate with ATC to keep separation from jets. And the oxygen rig does has to be more serious than a nasal cannula above 18000 ft.

Of course then there's these guys going to 90000 ft ... https://perlanproject.org/

[loeg]

As a glider it's probably easier with ATC to stay under 29,000 (RVSM), yeah?

[imglorp]

In practice, in the US, gliders aiming for wave would ask ATC for a wave window that comes with other constraints.

See page 8: https://www.norcalsoaring.org/uploads/1/0/0/6/100675970/high...