"One hell of a wake-up call !!"
Quote from a WW2 bomber crew after a mission over Berlin. A reporter had asked them about the flak going over town.

    That's right, you get shot at in these games. But that fire doesn't only come from the air, it comes from the ground. There are .50 caliber, 20mm, 40mm, and the dreaded 88mm triple A. In Aces High, you can add 5" naval gunfire, and 37mm fire to that list; both automated and player controled. AAA stands for Anti-Aircraft Artillery, the most hated foe of all pilots. More than one WW2 flier came home with a gaping hole in the wing or even worse... some never came home. A single shot from an 88mm triple A gun WILL wipe every aircraft in the game off the face of the planet. 88mm is roughly 3 ½ inches in diameter, and that thing is loaded with about 12 pounds of explosive. More or less an artillery piece powerful enough to knock out a Sherman tank at distances of over 3 miles. 5" guns are just that; 5 inches across and fitted with a VT fuse.
    The "German 88" started out as a simple yet VERY effective triple A gun around 1935. When the Germans found out that their current anti-tank guns wouldn't punch through the armor of British and French tanks, they used the 88. That happened in May of 1940. Even since then the 88 was used to pound tanks and aircraft, and the Allies hated it. Mass produced by such firms as Rheinmetal, it could hit and destroy enemy tank at nearly a mile, and nail enemy aircraft well over 25,000 feet. What about bigger guns? Well, the biggest thing you'll face is the original smart weapon. A 5 inch VT round. Developed in 1942, it's simply a standard 5" anti-aircraft round with a radar in the business-end. Once within 50 feet of a large metal object, or the ground, it explodes.
    Flak units can and will to their best to plant one of these massive shells right into the nose of your plane. You should be a little thankful that only a few places use these big guns. The average airfield will use everything up to and including 40mm triple A to get rid of you. This gun alone can remove most parts of planes with little trouble and without a wrench. Just beware they fire a lot faster than an 88 and tend to be more accurate. They will also explode after a little time in the air, usually near or on your plane. With Aces High they don't explode, but they can kill you just the same.
    The ranges for triple A is as follows:
 

    When it comes to getting out of the range of flak, the only thing you can think of is "RUN!!!". Don't do it, you'll end up dead. Just running from a flak site gives them a target that isn't moving in the sky, all it is doing is changing distance. You don't just run, you also maneuver. By banking left and right, and climbing sharply then leveling off quickly you can avoid most flak guns with ease.
    As long as you keep moving and don't stay still, you will be all right. Maneuver, climb, dive, jink (slide sideways by using the rudder), and roll but keep moving away from the site. What ever you do DO NOT set up a pattern, the gunners will figure it out and counter it with several dozen shells.
    Smaller stuff is a little harder to dodge. 50 caliber machine gun fire is only good for a short range, so it's easy to get in and blow up the gun before he causes too much trouble. 20 and 40mm cannons are harder to dodge because their shells travel a little slower and they blow up right next to you after a little time has passed. You can have some fun with this. Fly really low and at a fairly high speed, between the 20 or 40mm gun site and a town or a hangar. If you time it right they will do you a favor by damaging their own structure. All you have to do then is come around again and finish it off to get the points. Another way to get them to help is to fly over the enemy airfield at very high speeds and right down the runway. When the 40mm or 88s fire they will start putting holes in the runway, making it impossible for any aircraft to land on it.
    Other flak units are stationed inside cities and on ships. The ones stationed on ships tend to be a little more accurate than the average gunnery crew. And they show it, by lighting you up. But hunting flak sites is another thing all together. I've done a lot of flak hunting just so I could tour the country in my 109 without getting shot at. I've found the best aircraft for this job are energy fighters or heavy fighters. Both have fair maneuverability and more than adequate firepower, but the heavy fighters (Me-110 G2 and mosquito) seem to work the best.
    When hunting flak sites online it's always a good idea to have some backup. Even better; have 3 or 4 aircraft attack several flak sites that are close to each other. The limited number of flak sites have to pick a target, and as a result you and your wing men don't receive as much fire. If it was just you and one other pilot you'd be dead. Attacking 3 flak sites packing 88s is a good way to ruin your day.
    Another tactic for getting rid of these annoying but lethal guns is to dive bomb them. The Ju-87 Stuka is definitely the best for this task, and make sure to load it with 3 bombs. When it comes to dive bombing a flak site start very high, preferably around 10,000 feet, and dump the load when you get a good bead on the site. Or you can go one step better, but it's not one I recommend. You can assign a bomber strike on the whole area. Just carpet bomb the flak sites using the smallest bombs you've got and fly B-17 Gs. They carry the highest number of bombs and they can more than adequately defend themselves.
    By the way, flak is an acronym for Flieger-abwehr kanone. Translated from German it means anti-aircraft artillery. Panzer-abwehr kanone is anti-tank cannon.

Laser-guided guns: A comparison