guys, thanks very much for your inputs.

Look at below examples from Matrix: This is the cheapest available LH premium fare. If you force the inbound to Business Class, it will choose R fare, which is much more expensive than current combination. As you can see, the inbound is shown as A fare but the travel agent said this is a promtion fare from BA, which is effectively I fare so I fare rules apply, not A fare.


London (LHR) to Beijing (PEK) — Fri, Aug 25
[Overnight flight]
British Airways 39
Dep: 4:20 pm
Arr: 9:30 am
10h 10m
Boeing 777
Business (I)

Taipei (TPE) to Hong Kong (HKG) — Fri, Sep 8
Cathay Pacific 467
Dep: 3:20 pm
Arr: 5:25 pm
2h 5m
Airbus A330
Business (J)


Hong Kong (HKG) to London (LHR) — Fri, Sep 8
[Overnight flight]
British Airways 28
Dep: 11:45 pm
Arr: 5:35 am
12h 50m
Boeing 777
First (A)

Fare Construction (can be useful to travel agents)
LON BA BJS 1473.77IAPGB2 /-TPE CX X/HKG BA LON 1913.06AH4SUKP0 NUC 3386.83 END ROE 0.77624 XT 150.00GB 41.47UB 12.60TW 17.70G3 4.40I5 339.00YQ 3.90YR

Fare 1: Carrier BA IAPGB2 LON to BJS (rules)
Passenger type ADT, round trip fare, booking code I
Covers LHR-PEK (Business)

Fare 2: Carrier BA AH4SUKP0 TPE to LON (rules)
Passenger type ADT, round trip fare, booking code J, A
Covers TPE-HKG (Business), HKG-LHR (First)