Revenue maximizing airlines will hold back seats to keep them available for the higher revenue last minute fares. An airline never wants to sell out a flight 3 weeks in advance and lose out on last minute fares that are double or triple the average. Revenue maximized flights usually have load factors in the high 80s. Anything above that is a bit hard to repeat on long haul travel since the last minute cancellations combined with daily fluctuations in demand change.
Revenue management systems dont work like that at all. Revenue management is about monitoring the supply and demand of the fare bucks with the aide of historical data on the available inventory.
Lets look at the ORD-NRT 772 flight today, these are the fare buckets still available
F02 A02 J09 C09 D09 Z09 P09 Y09 B09 M09 E09 U09 H09 Q09 V09 W09 S09 T09 L09 K09 G09 N09
In two weeks the same flight looks like this
F06 A06 J09 C08 D07 Z04 P04 Y09 B09 M09 E09 U09 H09 Q09 V09 W09 S09 T07
In two months the same flight looks like this
F07 A07 J09 C03 Y09 B09 M09 E09 U09 H09 Q09 V09 W09 S09 T04
In four months the same flight
F06 A05 J09 C09 D09 Z09 P09 Y09 B09 M09 E09 U09 H09 Q09 V09 W09 S09 T09 L09 K09
As anyone can see from that the inventory available does not work the way you think it does. The inventory available is based upon supply and demand, how much the airline will charge for a ticket on a retail basis will vary upon the time of year, in popular times of the year prices go up as demand can exceed supply, in low months prices are lowered to sell the seat for some revenue, as that is better than none at all. Tickets sold on a contractual basis are often the same price year round regardless of the amount of time it was booked in advance, with no penalty for cancellation.
Airlines typically do not hold back making a sale at any time, they will even sell a ticket when the flight is oversold as the revenue management system knows about current and historical inventory trends, and blocked inventory with various retail and commercial channels. The airline also knows about contractual obligations it has for each flight. Some airlines also swap equipment around if needed to match demand, this is often done seasonally.
UA international load factors on average around 80% (that is reported in the December data, for 2016 and 2015), where I work it sits at around 85%. Everyone is in agreement that replacing the 744 with the 77W should improve the load factor and overall results, because it is a slightly smaller capacity Boeing that is cheaper to operate replacing another Boeing. But that logic cannot be extended to a slightly smaller capacity A350-1000 that is cheaper to operate replacing a 77W because it an Airbus replacing a Boeing. The horse and pony show you ant us believe is that the revenue management system will miss out on one fare sold at short notice sometime in the future, meanwhile you are paying the cost to operate the unused capacity every day.
You have not been able to show at all that the 77W is the right size for the route being flown, and frankly the only people would be able to are the back office staff deep within the airline that have access to all the data relating to the traffic load.
No one however is buying your overall thesis. The whole premise of the 77X is that even the manufacturer acknowledges the 77W is no longer competitive and it needed a major update. That does not mean the 77W is a bad aircraft, it is simply acknowledging that in 20 years technology moves on. I will put is another way which highlights the difference more effectively. The fuel burn difference between the 77W and A346 is about half as much as the fuel burn difference between the 77W and A350-1000.The industry works on very tight competitive margins, what is going to hurt you more on that anything else is paying higher cost to operate than your competitors. On long haul flying, around 60% of your DOC is fuel.
“Don't be a show-off. Never be too proud to turn back. There are old pilots and bold pilots, but no old, bold pilots.” E. Hamilton Lee, 1949