Dial-up does not make a plane go slower. Nor do you need to lead the plane more or change any gunnery behavior.
AH works in the way that what you see on your FE, usually happens. If you fly and fire at a plane turning infront of you, on your screen you hit him, he gets hit and it gets registrered.
At say 40Kbps, the reaction time on firing at flying object requires the gunner to lead the object more.
Not true, wether you use 19,2 baud rate modem dial-up or a 512kbs xDSL line doesn't matter.
Thus, delay in miliseconds (ms) to the server is not all that important, wether it is 50, 100, 200 or even slightly above that is not of all too much importance. What this shows in a fight is that when you lead an enemy in a deflection shot, and you fire and hit him, if your ping time is WAY up there he might see it as if you can't pull enough to shoot him although in fact you can, some delay.
What does matter is PACKET LOSS, this, you do not want. This is what causes warps, basicly some of the info from the server to you or the other way around (correct me if I am wrong on this) gets lost on the way from one another. Once the packets are re-established the AH finds out that "whops, the plane is actually there, not here as I thought a second ago" and it jumps the plane to that possition.
Airplane speed, is not affected what so ever in any way by your connection. The airplane speed is on your Front End (FE) meaning it is on your computer and is then sent away to the server. Having a slow dial-up connection doesn't slow down your airplane, it's not like the T3 users can press and LA7 to 400mph while the poor guy with the modem trying to run away can't reach more then 350mph.
If you are using a dial up connection, make sure you disable the compression for that connection. Can even slow it down to 19,2 baud rate as AH needs nothing more.
Hope I succeeded in making myself clear enough and that I understood your question.