Recently flew on Asiana from Seoul to Delhi - on an A330

I noticed that we took a very southerly route overflying Shanghai, Myanmar, Bangladesh, entering India around Kolkata and flying up to Delhi ... at a rough guess this is about 20% longer

Something like this - Great Circle Mapper (http://gc.kls2.com/cgi-bin/gc?PATH=icn-pvg-kmg-dac-del%0D%0A&RANGE=&PATH-COLOR=red&PATH-UNITS=mi&PATH-MINIMUM=&SPEED-GROUND=&SPEED-UNITS=kts&RANGE-STYLE=best&RANGE-COLOR=navy&MAP-STYLE=)

The direct great circle route from Seoul to Delhi would fly over the Tibetan plateau and high Himalays of Western Nepal approaching DEL from the North East.

I assume that the reason for the Southerly track was to avoid the high terrain ?

Do any commerical flights regularly fly over the high Himalayas ?

Probably a southerly routing to allow for the possibility of an engine failure en route and a safe drift down to a sustainable altitude before landing.

If a loaded A330 lost one over the Himalayas it's highest sustainable altitude on one engine may well be below the height of the terrain.

There may also be oxygen considerations in the event of a pressurisation failure, the emergency descent can only take place when it is safe to do so, if the aircraft had to maintain a high level for sometime before it could descend to, say, 10,000 feet it is possible it could run out of oxygen for the pax.

No they don't. The drift down for a twin would be well below the minimum safety altitude, even drift down for a heavy 747 would be. Passenger oxygen is carried for minimum duration. The Himalayas are so vast, enormous quantities would be needed for a pressurisation failure over them just to get to a safe area. Even B747s don't go over them. We used to skirt around the northern edge with 'oxygen escape routes' where if you had a pressurisation failure, there was a known rapid exit to a safe terrain area- 400 people hyperventilating get through a lot of oxygen! The Himalayas curve into the northern Pakistan mountains and become the Tien Shan mountains further north into Tadjikistan and Kyrgyzstan. Seeing them from a distance is scary enough! We used to fly around the northern edge to Urumchi in north western China.

Didn't United operate Chicago - Delhi via the Pole non-stop with 777s for a while? They could not have avoided flying over the Himalayas, could they?

To Rainboe's post.....saw exactly that a few months back on the NZ 744 between HKG and LHR, stunning views which helped to pass part of a 13hr sector.

Didn't United operate Chicago - Delhi via the Pole non-stop with 777s for a while? They could not have avoided flying over the Himalayas, could they? Judging by the route displayed on here (http://www.airliners.net/aviation-forums/trip_reports/read.main/116313/), it's a bit of a wimp out! Standard route ORD-UK then down over Kabul, and not anywhere near or over the Pole! Looking at my globe, the great circle would pass over Norway, therefore a more southerly route would be favoured to take advantage of the jetstreams across the Atlantic.

Thanks for the replies guys ... makes sense

Interestingly looking at the end of that Chicago-Delhi trip report the guy posts a shot of the Airshow map for the return flight which is polar ... but rather than routeing North out of Delhi it goes up NW over Pakistan and Afghanistan before turning NE after the highest terrain and proceeding then N towards the pole .. so the flight essentially makes a "detour" around the Himalayas