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Different ORD-HKG Routings  
User currently offlineWROORD From United States of America, joined Mar 2009, 972 posts, RR: 0
Posted (2 years 11 months 2 weeks 5 days 19 hours ago) and read 2920 times:

Flightaware is showing that UA ORD-HKG is flying westwards above Alaska and Siberia while CX is always flying eastwards over Greenland and Siberia. Why would they have two different routing for the same destination?

11 replies: All unread, jump to last
 
User currently offlinewilco737 From Greenland, joined Jun 2004, 9118 posts, RR: 76
Reply 1, posted (2 years 11 months 2 weeks 4 days 21 hours ago) and read 2827 times:
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Quoting WROORD (Thread starter):
Flightaware is showing that UA ORD-HKG is flying westwards above Alaska and Siberia while CX is always flying eastwards over Greenland and Siberia. Why would they have two different routing for the same destination?

I guess each dispatcher of each airline calculated the best way to fly. UA thought that routing is better while CX thinks the other routing is better.
ATC costs play a big role as well. It could be cheaper to do a detour, but then save a lot of ATC fees.

wilco737
  



It it's not Boeing, I am not going.
User currently onlinesunrisevalley From Canada, joined Jul 2004, 5220 posts, RR: 5
Reply 2, posted (2 years 11 months 2 weeks 4 days 16 hours ago) and read 2757 times:

Quoting WROORD (Thread starter):
Why would they have two different routing for the same destination?

Where the longitudinal distance between two points is 180 degrees plus or minus about 15 degrees the winds on the day could dictate an easterly or westerly routing. Essentially ORD and HKG are 190 degrees apart east bound or 170 degrees westbound. This time of the year with strong westerly winds could make the eastbound routing more attractive.


User currently offlineFabo From Slovakia, joined Aug 2005, 1219 posts, RR: 1
Reply 3, posted (2 years 11 months 2 weeks 4 days 6 hours ago) and read 2662 times:

If i may ask, to correct me or confirm,

but would this be dependant on cruise speeds? basically as I see it, the lower the cruise speed the higher the effect of the winds. So, say, UA is flying faster for whatever reason, so even with the winds it plays out better to take the westbound route, while CX is flying slower, so the winds have more effect proportionally and eastward is better.

The theory being extrapolation on that say if wind is 50kts on your head, if your TAS is 500kts it is not much but a nuisance, but if your speed is 250KTAS, its effectively making your trip a quarter longer. And if you are in a 50kts microlight you are better off going the other way round.



The light at the end of tunnel turn out to be a lighted sing saying NO EXIT
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17177 posts, RR: 66
Reply 4, posted (2 years 11 months 2 weeks 3 days 20 hours ago) and read 2562 times:

I'm not quite awake yet but winds are winds. It doesn't matter how fast you are flying. All other things being equal you want the route with best tailwind (or least headwind).

You can just think of wind as extra ground you have to cover. Doesn't matter if you airspeed is 300 knots or 400.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineKAUSpilot From United States of America, joined Jan 2002, 1963 posts, RR: 32
Reply 5, posted (2 years 11 months 2 weeks 3 days 16 hours ago) and read 2525 times:

Wind, temperature, and payload all play parts in routing decisions, as well as overlight permit costs as wilco737 mentioned. Wetbound routings from North America to Hong Kong typically have strong headwinds, with 100 knots or more not uncommon. Also, fuel temperatures can get too low if you follow great circle routings across the arctic in the winter time. Perhaps the payload was less on one of the flights allowing, the lighter plane to climb higher and take advantage of tailwinds more quickly, justifying route modifications.

Sometimes, a longer distance/time route must be taken to keep fuel temperatures above -40C on routes such as this. The reason for the longer route could be any of these things.


User currently offlinemusapapaya From United Kingdom, joined Apr 2004, 1098 posts, RR: 0
Reply 6, posted (2 years 11 months 2 weeks 3 days 1 hour ago) and read 2434 times:

Not having the chance to dig through erquipment both UA or CX uses, maybe this could be something to do with ETOPS? I remember CX using 777 on the route but is UA still on the 744?

regards
musapapaya



Lufthansa Group of Airlines
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17177 posts, RR: 66
Reply 7, posted (2 years 11 months 2 weeks 2 days 19 hours ago) and read 2377 times:

Quoting musapapaya (Reply 6):
Not having the chance to dig through erquipment both UA or CX uses, maybe this could be something to do with ETOPS? I remember CX using 777 on the route but is UA still on the 744?

Maybe but I don't think there are ETOPS restrictions on the route that would force a reroute for a 777-300ER.

CX also used 346 in the past. Was the routing then different? The plot thickens.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offline777ord From United States of America, joined May 2010, 548 posts, RR: 2
Reply 8, posted (2 years 11 months 2 weeks 3 hours ago) and read 2219 times:

Quoting wilco737 (Reply 1):

Can anyone provide any insight into what those ATC costs are? Are they calculated based off aircraft type/actual weight/pax numbers/ flat fee etc...?

Thank you!


User currently offlineFabo From Slovakia, joined Aug 2005, 1219 posts, RR: 1
Reply 9, posted (2 years 11 months 1 week 6 days 20 hours ago) and read 2153 times:

I believe generally MTOW plays a role, and planned route length through country. Some countries might throw more into that.


The light at the end of tunnel turn out to be a lighted sing saying NO EXIT
User currently offlinewarreng24 From United States of America, joined Nov 2005, 708 posts, RR: 0
Reply 10, posted (2 years 11 months 1 week 4 days 7 hours ago) and read 2007 times:

Quoting WROORD (Thread starter):
Flightaware is showing that UA ORD-HKG is flying westwards above Alaska and Siberia while CX is always flying eastwards over Greenland and Siberia. Why would they have two different routing for the same destination?

Just a guess, but a westbound routing permits the ability to divert to NRT if necessary. UA has a relatively large operation at NRT that is quite familiar with 744 operations.


User currently offlinen92r03 From United States of America, joined Jan 2010, 357 posts, RR: 0
Reply 11, posted (2 years 11 months 1 week 3 days 17 hours ago) and read 1923 times:

I don't think it has anything to do with ETOPS...I flew to HKG from ORD (UA 744) and EWR (CO 772) 4 times in '11 (June, July, Sept and Oct). Each time we went "up and over" very close to the north pole. 3 out of the 4 we were just west of it and once was just east of it. On the HKG to ORD/EWR returns, all except 1 were "up and over". The last one, on 10/31 went over Japan, south of Alaska and over Seattle, the Dakota's and into EWR.

I too would like to know more about overflight fees, etc.


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