The energy content of the max fuel load of a 747 is something like 2.5 gWh. The specifics of the site matter an awful in how fast that pays back.

So like if the extra generation were 1 megawatt with a capacity factor of 30%, you are looking at 7500 hours, less than a year, to yield that much energy.

That's a lot of assumptions, but the delivery flights probably average less fuel than that, and one of the benefits of size is that the capacity factor goes up.