I don't know where did this myth of cargo being a prime revenue source on longhaul flights originate, but it is just that, a myth. In the best of times (and let's ignore the current unprecedented and certainly transient situation) generic cargo rates from Singapore to Europe were around $2 per kilo, roughly half of the yield of an average economy passenger counted at 100kg with bags. Passenger aircraft are optimised for a maximum passenger load (plus baggage), so there is not much cargo space left with a full pax load at the edge of the range envelope, 3-5 tonnes at most. Add to this the variable headwinds, on a 14 hour sector to Europe the winter winds will reduce cargo capacity to nil (and sometimes even reduce pax load). With all this variability and uncertainty, critical cargo shippers will not chose passenger airlines, they will use dedicated freighter services of which there is plenty. Pax airlines are left with non-time critical generic cargo, which is good to fill underload if there is not a full pax load, but it is not a stable revenue to base a route on. Also this cargo is one-way only, on Asian routes the east-to-west cargo flow is about 10x the volume of west-to-east (where the winds would permit a higher load), thus usually pax flights carry very little cargo eastbound (cargo airlines manage this by operating continuously westbound round the world services).
PS. I'm no fan of Wizz, but I have to grudgingly admit that they are very disciplined when it comes to sticking to their cost model. Their adventure this past year with routes is a different story, we'll see what comes out of that.
Last edited by andrasz; 3rd Jan 2021 at 15:54.