The following are all the missions relevant to this achievement.
Training
Target Artillery
Supply Convoy
Evacuation
Training - Mclos Missiles
Capturing City
Attack Airbase
Destroy Communications
Training - Saclos Missiles
Lurking in the Trees
Attack Enemy Squadron
Evacuation 2
Jungle Air Support
Night Silent Attack
Pilots Down
Tanker Attack
Capture Oil Platform
Submarine in Trouble
Night Silent Attack mission help.
The tricky one. First you need to infiltrate the base by not raising your altitude above 60m. You have 2 allies that fly much faster than you, so at the next checkpoint you will have to be quick.
You need to destroy the helicopters before take off. You will be much further behind than your allies, so increase you altitude by enough to see the targets in the distance. Press

twice to zoom right in and unleash your tickets on each helicopter. One should be enough for each. The next objective sees the whole airbase on full alert. You will be under heavy fire including tickets, so use your flares when needed.
Capture Oil Platform mission help
This is a highly irritating mission, that's split into 2 oil platforms that you need to capture. The 2nd being the reason for the difficulty being high. Your door is jammed forcing our to use your high caliber weapons. One shot can destroy the oil tankers thus failing your mission.
I found the following to be easier. Hold down your

button to manually aim with the white crossbar and use the

to shoot. Kill all the troops that are marked. I would zoom in with the

button twice and click the

to get the best viewpoint. It's hard due to the oil tanks being in the way of things, but patience and perseverance are vital to completing this half of the mission. In my opinion, this is the most difficult mission of the campaign.