The following is the most commomn situation on different routes, but bare in mind, for various reasons, you can encounter an empty flights on busy routes and vice-versa... for example: on 1st of Jan DXB-DME goes with no more than 15 pax, but the return leg on the same date is always overbooked; DXB-CAN-DXB flights are overbooked and go 777-300 2 class with 400 pax in economy, when there is a fair; you have to book at least 6 months in advance DXB-MLE flight in First or Business if you want to fly 18-22 DEC etc...

ALWAYS FULL:
JFK 201, SFO and LAX in Y
JNB, DUR, LOS, LAD, MRU
LHR (ex-029), MAN, BHX, GLA, MAD, AMS, HAM, FCO, IST
JED, IKA, LHE, PEW, ISB, INDIA in Y, BKK, HKG, MNL in Y, DAC, ICN, SYD (ex-414), MEL, BNE, AKL

ALMOST ALWAYS FULL
YYZ, GRU
CPT, NBO, CAI, BEY, DAM, AMM
CDG, FRA, MUC, DUS, VIE, ZRH, MXP, VCE, DME
KIX, NRT, PVG, CGK, PEK, CMB, KUL, PER

NEVER FULL
DKR, KRT, SAH, MCT
NCL, NCE (but fare is double comapring to other EU destinations)

ALWAYS (or almost always) FULL FIRST CLASS
LHR 001, GVA, ZRH, BKK 384, NRT, ICN, SYD 412, JED, JFK 201, LOS

*the list is not complete