ORIGINAL: AcePylut
Ok, so studying the Japanese aircraft fighters.... I figure I don't need to bring forward any of the aircraft that arrive in '42.
You don't, but if the plane you want to accelerate is at the end of an upgrade path, you should begin with the earliest R&D in the line. For instance, if you want to accelerate the Tojo IIb, start researching the IIa instead.
Why? Because of factory repair times. Before you can research anything you need to repair the factories, and the earlier the model, the faster they do. Once repaired, you can upgrade them without damage to the next model.
In other words, if you want the Tojo IIb, begin the game by ordering 30 factories (or any multiple thereof) to research the IIa. They will repair much faster than if you ordered them on the IIb, and once they are repaired, you can upgrade them to the IIb, and get more advance. You cannot do this for the George, which is at the beginning of a line, but for the Tojo, Oscar, Tony and Zero (note the Rufe upgrade path...) this is the way to go.
Francois