Altitude India/Paksitan
 

Coming back from Bangkok to London yesterday as SLF initial cruise was FL340 then, somewhere over India 360. Approaching the Pakistan border we seemed to turn onto a more SouthWest heading (trying to work that out from AirSho is a bit hit or miss) and dropped to 350. Then turned Northwest over Afghanistan (and lots of other 'stans in what used to be Southern Russia that I'm ashamed to admit I can't recognise on a map yet) and up to 380.

It's many years since I flew back from the Far East. My travelling has been confined to Europe, USA and one trip to Argentina but everywhere else the trend always seems to be that the altitude goes up as the flight progresses (which I understand is because engines become more efficient and as fuel is burned weight goes down and therefore climb is possible).

So, why the descent as we went from India to Pakistan? A difference in how flight levels are allocated or is it that the new heading meant we had to use a different level?

...Airspace can become crowded
 

It has to do with opposite/crossing/converging traffic separation criteria.

Without breaking it down region by region.....

F/L 340 then F/L 360 Bangkok across India is normal RVSM levels with a routine step climb between the two. Then, back to ICAO F/L 350 for some of the 'stans', then 11600M (close to F/L 381) in some of the 'stans' where metric altitudes still prevail, then (thank God) across Europe where RVSM and sanity prevail.

A bit simplified, but that's the essentials. Hope that helps.

PS. I fly this route several times per month and the only ex Southern Russian state name that I can remember is Georgia. Too many stans to remember.