As mentioned above, it is usually not a good idea to attack at a steep diving angle. This is a mistake that many new players do. After such an attack you either blow lots of E in the pull out, or end up running away (aka "extending" to infinity) at 500 mph - which may be desirable for some players, but I think it is stupid.
Having said that, sometime it is called for - perhaps trying to shoot a bad guy off of your squad mate, sometimes when attcking bombers from the top, and for some planes, even shallower angles can lead into trouble when starting from high speeds (P-38, Mossie, 109...). When you know your plane, you will be alert to your speed and be ready to step on the breaks before hitting the critical limit. In all planes the first thing you do is throttle back to min. If that is not enough, some planes have "gadgets" that can help them to maintain the speed or assist with the pullout:
- P-38 have the dive flaps. The dont slow you down much, but will prevent the elevator lock and will allow you to pull out of the dive. You have to engage them early enough because beyond a certain point even they won't help.
- P47D40 also have dive flaps.
- Mosquitoes can open the bay doors, but only if you had bombs inside before taking off (they dont have to still be in there, but if you took off with an empty bay you will get a message that says you do not have a bomb bay... go figure.)
- SBD has a very cool and effective dive break.
- F4Us can pull the gears out, but I dont remember what is the maximum allowed speed for that and if it is relevant at high speeds.
In all planes you still have controls that will help you maintain your speed and allow a pullout - rudder and elevator trim. At high speeds the rudder is progressively less effective at yawing the plane, but it does create a lot of drag. In 109s, mosquitoes, A20s... etc, I will often be riding the rudder while diving in order to prevent over speeding. Combat trim is a suicide device! if you use it, turn it off when diving either by using the toggle key, or by manually trimming which will cause it to toggle off. Trim nose up so you will have to keep pushing stick forward in order to stay in the dive - this way you know you can still pull out of it.