Actually, I find it better to takeoff from a runway in the rear area that is on a mountain top. That extra 5,000-8,000 feet will save you time. If you take off from somewhere closer to the front, your just going to have to fly away from the fighting untill you get enough altitude anyway.
And I find none of the runways long enough. I don't think it is the plane's fault, just he short runways we have. I just continue building up takeoff speed in the bumpy grass. Alot of airfield of the day were grass anyhow, and the lancaster has some huge tires for that.
H, S, N, and the rest allow to choose which runway you want to start on. With vehicles you can teleport accross vast distances using those buttons, as the vehciles don't start on runways. So, to make a tank attack on an enemy base to the west, choose a tank and hit the "W" key to start you out damn near on top of the enemy base.
Hans.