Hi,

Apologies if this is in the wrong board; please move if there's a more appropriate place

I couldn't find much information about how combinability rules are supposed to be evaluated on fares. I was looking at a SEA-CHQ flight, which came up on ITA as:

SEA-FRA - Fri, Jul 25 (UA 8718)
FRA-SKG - Sat, Jul 26 (LH 5928)
SKG-CHQ - Sat, Jul 26 (A3 728)

CHQ-ATH - Sun, Aug 3 (A3 345)
ATH-FRA - Mon, Aug 4 (LH 1285)
FRA-SEA - Mon, Aug 4 (UA 8717)

ITA splits it up into two fares:
Fare 1: Carrier UA YR1 SEA to ATH
Fare 2: Carrier UA SHX21NCE ATH to SEA

The YR1 fare seems pretty unrestrictive, so I'm not really concerned about that one. However, the SHX21NCE fare does have a number of restrictions, including combinability:

ROUND TRIPS/CIRCLE TRIPS
FARES MAY BE COMBINED ON A HALF ROUND TRIP BASIS
-TO FORM ROUND TRIPS
-TO FORM CIRCLE TRIPS
A MAXIMUM OF TWO INTERNATIONAL FARE COMPONENTS
PERMITTED.
PROVIDED -
COMBINATIONS ARE WITH ANY FARE FOR CARRIER UA/LH/LX/OS/
SN/AC PUBLISHED FOR TRAVEL VIA THE ATLANTIC.
COMBINATIONS ARE WITH ANY FARE FOR CARRIER UA/NH
PUBLISHED FOR TRAVEL VIA THE PACIFIC.

Does this mean when evaluating the RT combinability, we only reference the transatlatantic fare, which is on UA/LH? If so, is the A3 fare from SKG-ATH ever supposed to be evaluated in any combinability setting? Or is it considered an add-on, since the fares are just SEA-ATH, not SEA-CHQ?

Thanks,
Roger