Realistic is fun isn't it? Add a glitchy achievement and it doubles the fun. Don't worry, Failed is here to help!
To make this achievement easier you can make a Custom Difficulty which the game thinks is Realistic but falls somewhere between Simplistic to Realistic.
First you'll want to set up a Custom difficulty like this:
Walkthrough:
Take Off and head to Waypoint
Straight away fly in a big circle so your behind your bombers. This will give you a great opportunity to shoot fighters down as they chase your bombers.
Destroy aircraft attacking your bombers, try to stick with the bombers (or the achieve won't pop), you have 18 and if it drops to 8 you fail.
Don't break off to chase anyone and if they're falling out the sky with black smoke, don't follow them down. You'l get the kill when they hit the water.
Destroy 5 planes as fast as you can, the achievement is slightly glitchy and sometimes doesnt' pop. Wether this is because your too far away or because the bombers have reached the boats i'm unsure of.
Achievement pops straight away, but it took me 3 goes.