Topic Author
Posts: 894
Joined: Thu Jun 03, 1999 12:38 pm

IFR Cruising Altitudes

Wed Jun 14, 2000 1:05 pm

What are the designated cruise altitudes for Class A airspace in the US for eastbound and westbound routes?
Posts: 29881
Joined: Wed Jul 07, 1999 11:27 am

RE: IFR Cruising Altitudes

Wed Jun 14, 2000 4:41 pm

Ok...Luckily I am at work so I can go off my handy dandy cheat sheet.

For FL180 to FL290

0 to 179 degrees, Every 2000 feet odd numbers...19000,21000,23000,25000,27000,29000

For 180 to 359 degrees every 2000 feet even.


If you are above Fl290 it is every 4000 feet

I should add there are a lot of areas that are now experimenting with reduced minimums so these rules don't always apply.

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Joined: Fri Mar 16, 2007 1:29 pm

RE: West Even/East Odd <FL280//RVSM

Thu Jun 15, 2000 12:35 pm

RVSM has been in place on an experimental basis on the NAT for 3 years. It has just been introduced on the Pacific OTS. After several more years of freedom from aluminum rain, RVSM will probably be introduced into mainland Europe and the USA.

Reduced Vertical Separation Minima changes those limits above FL280 mentioned by L-188 above from 2000 to 1000' separation of opposite direction traffic.

In the old days of pressure altimeters, given the fact that atmospheric pressure changes are not the same at high levels as they are closer to terra firma, and given the state of development of air data sensing systems, it was felt that an added 1,000' was necessary in the higher flight levels. Now with the development of ADC's, accuracy is easier to attain. Hence the experiment with RVSM.

And it's working. It's an exciting time to be in aviation. Changes are occuring much more frequently than in the past.

Other kinds of change though may not be so progressive (LAHSO/SIRO). Another thread!

Best Regards,


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