I don't think DL made any mistake. Unlike some other carriers, DL didn't order the A350 as an ULH airliner. They had the B77L as an ULH airliner. So they simply didn't need range and they chose to reduce their operating costs by having a lower MTOW.
They did make a mistake. Their original 268t frames had problems flying relatively short TPAC routes, such as DTW-PEK; they had to up-rate them to 275t to be able to haul a profitable payload.
A350 is underwhelming as a regular TPAC aircraft, let alone an ULH airliner.
Zeke just a few posts above gave his data point for A350 flying IAD-HKG without any problem.
You also largely misinterpreted the BTS data I showed before.
Why are you constantly trying to mislead people here, arguing A350 is significantly worse than 787?
Of course Zeke is talking about a CX A350 (I.e. using CX configurations, with CX operating rules, CX routes and CX operating margins). While a perfect A350 can fly a very long way empty, once it is utilized as the airline wishes, the reasonable capabilities decrease. A 77L flew the long way from HKG to LHR (22 hours) on an exhibition flight, but has a hard time flying 18 hours during normal airline operations. This fleet decision has as much to do with how the airline operates as it has to do with how the airplane operates.
Just some things to think about...
Logistically, the 777 Pilot Base in LAX is a direct result of the SYD flight, if the 777 is removed from that route, the pilot base would likely have to be switched to an A350 Base (I.e expensive)
As far as revenue, Until the 777 reconfigurations, the 777 held 15% more D1 seats than the A350 and an equal number of “premium” seats. With the reconfigurations, the 777 has 14% less D1 seat, but double the number of “premium” seats (28J, 48W, 90Y+, 122Y) vs the A350 (32J, 48W, 226Y). DL considers anything other than standard economy to be a “premium seat”.
Additionally there is a difference in both the cargo volume and overall weight the aircraft can carry (is the hold full of gold bars that weigh a lot or Koala Fur that takes up a lot of space?) based on the ratio of Available space to available weight it could tip the scales one way or the other.
As far as fuel is concerned, both aircraft should be near their maximum ability, holding at least 16-17 hours of fuel, and the most “problematic” areas of fuel occur at both ends of the route between. The plane has to have the ability to fly from 2.5-4 hours (between HNL-LAX/NOU-SYD) with the worst case scenario of A) a single engine, b) depressurized or c) single engine while depressurized. As far as HKG-IAD is concerned, an engine failure 2.5 hours before landing means a diversion to an inconvenient airport that is maybe 1 hour away.
With all those factors considered, (and I can’t speak to the specifics that made DL decide one way or the other) at the current time, DL has decided that their 77Ls are best used on the SYD-LAX route vs thier A359s. If CX was operating the route, CXs revenue curve and operation requirements might come up with a different solution.