Thomas Borchert writes:

Nope, and I don't think they use airdata, either. Also, their cones are
aruond airfields, not the aircraft. And they do take field elevation
into account. See
http://docs.controlvision.com/pages/cones_of_safety.php

Oooooohhh...now I get it. I was thinking more in terms of "here are all
of the places you can glide *now*" not "wait until you're over here to
lose an engine." It would be more of a realtime extension to the
"nearest" button functionality.

O.k., so my idea really isn't affected by their patent. I still hate
software patents.

Thanks for the clarification.

BTW, I take issue with this.
Around each airport there is a region of airspace from which
an airplane can safely glide to a landing. We refer to this
space as the Cone of Safety.
My wife likes to point out that there was a time when landing at an
airport was the exception - certainly not a requirement for a safe
landing.

--kyler