Cruise height tradeoffs?

Date:         27 Aug 99 14:03:34 
From:         "Peter Kuykendall" <Peter_Kuykendall@bigfoot.NOSPAMcom>
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I'm wondering what the tradeoffs are that have established the modern
airliners cruise altitude at ~40K ft.  Why not 20K or 80K instead?  At first
glance it would appear that doubling altitude for long haul flights would
substantially reduce drag but perhaps there are mitigating factors such as
increased wing area, engine size, etc. that may offset the savings?  Or is
it limited by time to descend after a sudden depressurization?  Or maybe
something else entirely?

I can see that long climbs may not make sense for short flights but I would
imagine that a transpacific run (for example) would be so long that the
extra climb would be trivial on a 13 hour flight.

Any input is appreciated.  Thanks!

-- Pete in Laguna Niguel, California USA
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