for QR -1000 there is a little batch of 3 windows alone, right after the 2nd door, that doesn't exist on the -900. Count of windows between the 2 1st doors for QR -900 and -1000 is almost too similar..
for CX I guess, we need to count the windows, 15 for the -900 and 22 for the -1000...
I guess I know what's happening now if you look at the premier pic like this one
Doesn't help when the landing gears are retracted. Window counting is the surest way to tell them apart.
From an Aviation Week article "Flying The A350":
The V1 takeoff decision speed was 132 kt. indicated airspeed (KIAS), rotation 133 kt. . . . .
Now I'm really curious to find out how you are going to count windows when the gear is retracted . . .
Haha, Ok! Counting windows is not the easiest thing to do. But honestly, I think it is not too hard to tell them apart by eyeballing the fuselage length. It is a bit like distinguishing an A346 from an A345, or a B77W from a B77L.