Date: 13 Mar 98 03:35:12 From: email@example.com (James Matthew Weber) Organization: GoodNet References: 1 2 3
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On 03 Mar 98 03:12:47 , firstname.lastname@example.org (Larry Stone) wrote: >In article <airliners.1998.362@ohare.Chicago.COM>, Paul Hathaway ><Paul_Hathaway@ML.Com> wrote: > >>Simplest way to think of it is that the time used to attain cruise >>altitudes is short in relation to the time spent en route at the fuel >>efficient altitudes. The 'extra fuel" used to get to 35,000 feet is >>small compared to the fuel saved by cruising there for 4,5, or 6 hours. > >And for really efficient planes, you don't even need to be up there that >long. I have numerous times flown SFO-SNA in a 757 at 41,000 feet. Total >flight time is in the 1:00 to 1:05 range. Traveling at FL410 on SFO SNA is only coincidentally related to fuel consumption. It has everything to do with getting there on time. Relatively few airliners can fly that high, so it avoids congestion.. It gets you up and over the traffic. It saves fuel because it avoids ATC delays. It is very unlikely to be the optimal altitude for the A/C however. The aircraft has to be at extremely low weight to make it attractive to fly up there. You will find the odd 767 and 757 up there, along with 747-SP's at end of cruise on a very long haul flight. Airbuses never get that high, and neither do 737's. It is very rare for 777 or 747's to be up there.