I asked this elsewhere, but since a lot of you use Flightaware.com , I'll ask again here. I have been watching aircraft on the flightaware.com and noticed that a lot of commercial aircraft don't seem to follow the RVSM rules. For instance, Aloha Air Flight 486 from PHKO to KSNA filed for a flight level of FL390, but actually flew at FL40, AAL38 from KDFW to LSZH filed at FL310, but flew FL340. I'm assuming this is because of winds, but how strict are these levels? This was a trans ocean flights but I've seen this on flights everywhere.Brad2 miles from KELP/KBIFhttp://www.hifisim.com/images/asv_proud_supporter.jpg

Hi Brad,As you already said, the flightplan for AAH486 was filed according to RVSM rules, but was flown at a different altitude. Most probably, ATC asked them to climb 1000 ft higher because of other traffic at FL390, and no oncoming traffic at FL400. Actually this is a very common occurrence in oceanic airspace, because between specific times, the majority of aircraft will fly in the same direction. This is illustrated best by the NATs and PACOTS. For example, today's westbound NATs are valid 1130-1900 UTC. Between these times, the whole block of flight levels between FL310 and FL390, including the even levels, is reserved for flights going westbound. This causes a lot of flights to be given an even cruise level by ATC, where you would expect them to fly an odd one. The actual level over the Atlantic and busy parts of the Pacific usually depends on other traffic, where in other areas optimum cruise performance and weather are the main factors to consider. Finally, deviation from the filed RVSM level is always done on ATC discretion (except for emergencies of course)...Cheers,http://home.planet.nl/~duijn181/cu2/koen.jpg

Koen,Thanks for the detailed explanation. I really appreciate it. Brad2 miles from KELP/KBIFhttp://www.hifisim.com/images/asv_proud_supporter.jpg