You can also use the "Wind" function while offline to improve your climb rate significantly by setting a huge updraft situation. That will make even a bomber climb at better than 4K/minute. Just turn off the protectfriendlyobjects parameter so you can bomb stuff that's yours.
Specifically, launch a bomber near any target you wish (launch from a field maybe only 1 sector away). Don't bother to launch a formation of bombers, it offers little in the way of real "training" value. Once airborne, go level and gain some speed, no need to gain any real altitude. Get the gear and flaps up. Then, turn on the auto-angle autopilot (SHFT-X) while fairly level so that the plane will not change the nose angle much in the next thing you do.
Open the clipboard, click on settings, and then on the wind button. That will open a wind control screen. In the box called "Rise" type in a number between 0 and 127 (the more the better) which will start a wind rise. Then, press ok to get out of the wind control screen and you will find your plane will jump upwards carried by the updraft. Once near the desired bombing altitude, open the clipboard, setup, wind, and press the NO-Wind button to cancel the wind OR in the case where you want to not cancel all wind, just put 0 in the rise and press ok.
Then you should be at altitude in very short time and you can bomb on any map and not have to worry about the airstart thing. The same thing works with fighters too if you want to get to high altitude quickly.
-Soda
AH Trainer
The Assassins.