Tom Sixkiller wrote:

[ heated airliner windscreens]

Why do they run them at altitudes that birds don't fly?

I assume your question is rhetorical, but the range of altitudes at
which birds may be found is far greater than most people suspect. I have
seen them 14,000 msl over the lower 48, and that is no record.

Other reasons: ice & snow, FOD (balloons and their payloads, kites,
model aircraft, wind- and vertical current-borne objects and material),
and of course the ever-present possibility of mid air collision -- all
of which must be considered at all altitudes within the operating envelope.

But these considerations have little to do with the advisability of
preventing skyjacking by any means necessary, including the use of
firearms by Federal Sky Marshals. As a cockpit crew member, a blown out
window is something I can deal with -- a medium sized problem: a team of
terrorists controlling the cabin is going to be a much bigger problem,
and it will have ramifications well beyond anything we are likely to
include in our discussions here.


--
Jack

"Cave ab homine unius libri"