Wehn calculating the distance, there are spots that do not use the airport-to-airport distance. This is typically cities with multiple airports. If you know of these spots and use GC, you get the right distances.

The spots I know of that can tip you a few miles either way are these:

Seoul = SEL
London = LON
Tokyo = TYO
New York = NYC
Shanghai = SHA

And if you look in the GC for your LHR-NRT-PVG vs LON-TYO-SHA routing (latter beign correct for mileage), the you get this: http://gc.kls2.com/cgi-bin/gc?PATH=l...%0Alon-tyo-sha

For the lazy ones, 7093 miles vs 7064 miles, which in this case makes of breaks your 29.000 mile limit. If anyone else knows of the correct coterminals in use for other airports, then let s start getting them in a list? This is why people sometimes get differing mileage from GC vs an airline or TA's official numbers.

I suspect this also will affect Bangkok once the new airport comes online

Another cozy little example is this one:http://gc.kls2.com/cgi-bin/gc?PATH=y...2C+yvr-icn-sin

YVR-SIN is 7967 miles, YVR-ICN-SIN (fly the segments on the same flight seperately) is 7975 miles and the correxct way of measunging this is YVR-SEL-SIN at 7974 miles, in case you need that one magic mile in your calculation

Maybe someone here with better knowledge than me can answer wether measuring via co-terminals is mandatory or wether once can choose the actual airports?

Or to answer the original posters question: is the any slakc to be cut? I've had itn's for 29003 miles denied by SK. According to them there is not a single yard leeway.