This is getting wierder by the moment.

I talked to my TA, which said sa far as they knew, it was at thrier discretion to use either to the customers adavntage, but knew of no specific rule. Then I talked to a regualr SK TA which claimed their system showed no difference in mileage wether measuring cities or specific airports, and that measuring should always be done by city/co-temrinal code, and ticketing on the specific airport code, i.e. you measure LON-TYO, but ticket LHR-NRT.

Then she got confused and talked to their (SK) RTW-desk, which claimed that neither of the the measurements for OSL-LON in GC (http://gc.kls2.com/cgi-bin/gc?PATH=osl-lhr%2C+osl-lon ) are correct, and the official number is 736.

Not wanting to give up, I went off to get the numbers for NRT-ICN, which gives even greater cause for misrepresentation:

My TA says: TYO-SEL 759nm
GC says: TYO-SEL 732nm
*A RTW calc: TYO-SEL 759nm

Also, *A RTW calc quietly gives the same for TYO-SEL as for NRT-ICN. What concerns me is that the official *A mileage for the city codes do not match the actual distances.

Given what I've seen so far I conclude this:

* Co-terminals are used for mileage calculation, but airport code is used for ticketing.
* Co-terminals are present in GC, but seem to give different distances than the official count.

Conclusion: GC is nice for figuring the length give or take a few miles, but cannot be used for accurate mileage once you get close to the limit

(I.e. my first port further up was right about co-terminals, but as long as *A and GC have different ideas of the locations/lengths, it doesn't really matter that much).