http://tinyurl.com/y394h58

That covers jet planes, yes. But why have all propeller-driven
aircraft
been grounded as well?

People are trying to tell me that gliders are also grounded.
That is total nonsense. For heaven's sake, they don't *have*
engines, and they are unlikely to get up to 55,000 feet. The UK
height record is only 38,000 feet.

Anne