Traffic from Alliances

[rybob1]

Just curious,

I'm curious how alliance traffic increases are calculated.  I'll use a couple examples to demonstrate my question:

Alliance 1:
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3 airlines, based in SFO, LHR, NRT
None of the 3 airlines share any connecting cities (meaning in a real world, no connecting opportunities)

Alliance 2:
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3 airlines, based in SFO, LHR, NRT
all three serve the three airlines base cities, with at least 1 frequency per day

I realize that the game doesn't offer codeshare/connections, but how is the extra traffic generation calculated?  Is it based on the # of potential connecting cities and the number of routes and their capacity (#2), or is it an arbitrary calculation based on the ASM across each airline route network (#1)?  Or something completely different?

[Kontio]

I've always thought it is just a CI boost.

[Sigma]

It's essentially just a CI boost and it's supposed to be a fairly small one at that.

Frankly I've never noticed the slightest increase and I've tried several times to drop in and out of an Alliance (of a 100% rating) to determine what, if any, impact to my numbers that there was.