I'm following the tip of finding the first two segments first.
This map of all (did I miss anything?) direct flights from C3 to C1 will help others who tries to crack this riddle
Code:
C3-C1 direct:
SIN: SEA, SFO, LAX, EWR, IAH
HKG: YVR, SEA, SFO, LAX, DFW, ORD, YYZ, IAD, BOS, EWR, JFK
NRT: YVR, YYC, SEA, PDX, SFO, SJC, LAX, SAN, DEN, DFW, IAH, MEX, ORD, ATL, DTW, IAD, JFK, EWR, BOS, YUL
PEK: YVR, SEA, YYC, LAS, SFO, SJC, LAX, TIJ, ORD, DTW, YYZ, IAD, YUL, JFK, EWR, BOS
PVG: YVR, SEA, SFO, LAX, DFW, ORD, ATL, DTW, YYZ, JFK, EWR, YUL, BOS
ICN: YVR, SEA, LAS, SFO, LAX, DFW, MSP, ORD, ATL, DTW, YYZ, IAD, JFK, BOS
DEL: YVR, SFO, ORD, YYZ, IAD, EWR, JFK
BOM: YYZ, EWR, JFK
TPE: YVR, SEA, SFO, LAX, ONT, IAH, ORD, YYZ, JFK
MNL: YVR, SFO, LAX, YYZ, JFK
No direct flights:
HAN
DPS
CGK
ALA
TSE
KUL
BKK
Here's my log:
via SIN to SEA: no routing found
via SIN to SFO, LAX, EWR, JFK, IAH: expensive EOE fares (SQ)
via HKG to YVR, YYZ: expensive EOE fares (CX/AC/EU carriers.)
via HKG to SEA, SFO, LAX, DFW, ORD, IAD, BOS, EWR, JFK: expensive EOE fares (CX/EU carriers)
via TYO to YVR, YYZ, YUL: expensive EOE fares (AC/SU/NH/EU carriers),
expensive PA-routing JL fares (MOW-YVR)
via TYO to SEA, PDX, SFO, SJC, LAX, SAN, DEN, DFW, IAH, MEX, ORD, ATL, DTW, IAD, JFK, EWR, BOS: expensive EOE fares (DL/SQ/SU/S7/EU carriers)
via PEK to YVR, YYC, YYZ, YUL: expensive EOE fares (CA/AC/HU/EU carriers)
via PEK to SEA, LAS, SFO, SJC, LAX, TIJ, ORD, DTW, IAD, YUL, JFK, EWR, BOS: expensive EOE fares (VS/DL/MU/EU carriers)
via PVG to YVR, YYZ, YUL: expensive EOE fares (VS/MU/CA)
via PVG to SEA, SFO, LAX, DFW, ORD, ATL, DTW, JFK, EWR, BOS: expensive EOE fares(MU/CA/DL)
via ICN to YVR: expensive EOE fares (OZ/KE),
expensive PA-routing KE fares (origin MOW, LED)
via ICN to YYZ: expensive EOE fares (OZ/KE)
via ICN to SEA, LAS, SFO, LAX: expensive EOE fares (OZ/KE),
expensive PA-routing KE fares (origin MOW, LED)
via ICN to DFW, MSP, ORD, ATL, DTW, IAD, JFK, BOS: expensive EOE fares (KE/AA/DL)
via DEL to YVR, YYZ: expensive EOE fares (AC/SU/AI/EU carriers)
via DEL to SFO, ORD, IAD, EWR, JFK (AI/VS/UA/EU carriers)
via BOM to YYZ: no routing found
via BOM to EWR, JFK: expensive EOE fares (UA/AI/EU carries)
via TPE to YVR, YYZ: expensive EOE fares (CI/BR/AC)
via TPE to SEA, SFO, LAX, ONT, IAH, ORD, JFK: expensive EOE fares (CI/BR)
via MNL to YVR, YYZ: expensive EOE fares (PR)
via MNL to SFO, LAX, JFK: expensive EOE fares (PR)
Each of the above combinations was checked using
LON, DUB, AMS, PAR, BRU, FRA, BER, VIE, MAD, LIS, BCN, ROM, OSL, CPH, IST, MOW, LED, KBP as origin points. So far no luck.
I'm using the following input data (with reference to the original conditions):
1. This is a construction, so a single ticket ("Safe construction"). Separate tickets would not qualify.
2. All flights are direct, but not necessarily non-stop ("4 segments")—this means fuel stops are allowed (e.g. SQ52 SIN-MAN-IAH is valid), but connections are not (since each leg is a segment).
3. TLV, DOH, DXB, AUH are out of the question (terminology C1.5 used thus these would be C2.5, not C3).
I tried to interpret these as precise as I could, still maybe I got one of these wrong?
I have also tried to use different C3 cities to arrive and depart from (e.g. arrive in PEK, depart from TYO), but I got no luck at a few few tries and the amount of possible combinations given the number of C2 airports to check is so significant it's not reasonable to check all of these. Still, should I maybe dig in this direction? Or maybe I simply missed a C3 (or C2) airport?
I already asked people who figured this out in PM for help but no replies so far (as usual). Can anyone please make an exception and help me in PM on what I'm doing wrong? I've spent a full day today (in vacation) not leaving the hotel trying to crack this one. Would really appreciate it.