Isn't it odd thousands on heading 001 to 180, and even thousands 181 to 360 heading?Help me out, I always get this wrong in my head.RhettAMD 3700+ (@2530 mhz), eVGA 7800GT 256 (Guru3D 93.71), ASUS A8N-E, PC Power 510 SLI, 2 GB Corsair XMS 3-3-3-8, WD 250 gig 7200 rpm SATA2, CoolerMaster Praetorian

East Odd West Even for East/West flight separation and East/west RVSM...So, for the airspace following E/W rules, you are correct...Beware of the territories implementing N/S separation rules...Andrew

What has been described is the requirenent in the USA.In the UK, for example, the rules are different. For IFR flights above 300ft (or the appropriate transition level) and below 24,500ft there is a quadrantal rule based on magnetic track:less than 90 - odd thousands90 but less than 180 - odd thousands + 500ft180 but less than 270 - even thousands270 but less than 360 - even thousands + 500ft.For flight at levels above 24500ftless than 180 - 25000, 27000, ....41000 or higher the interval becomes 4000ft180 but less than 360 - 26000, 28000 ....43000 the interval becomes 4000ft.These only apply to IFR flights. There is no requirement for VFR flights to obey these rules although it is recommended that it does.

If you're after the U.S rules., you're off by just a degree.14 CFR 91.159 VFR cruising altitude or flight level.Except while holding in a holding pattern of 2 minutes or less, or while turning, each person operating an aircraft under VFR in level cruising flight more than 3,000 feet above the surface shall maintain the appropriate altitude or flight level prescribed below, unless otherwise authorized by ATC:(a) When operating below 18,000 feet MSL and