Call of Duty

Mission 3: Reactor
In this guide I found 2x Bomb Drones, 1x Cruise Missile and 1x Precision Airstrike worked in getting my achievement to pop.

Bomb Drones:
Parachute into the Mission head North East towards a supply drop tangled up in a electricity pylon, where you'll find the first Bomb Drone. Now head South East to a white/blue cabin where you'll find a second Bomb Drone. Use both of these on the closest helicopter to the East.

Cruise Missile:
Directly behind you to the West, beside this blue/white cabin is another supply drop with a Cruise Missile in it. Immediately use this Missile to take out the helicopter on the West side of the map.

Precision Airstrike:
Now head South towards the last helicopter, the large hanger to your left has another supply drop hanging off it (beside the letter "A"). This drop has a Precision Airstrike in it, pick that up and use it on the last helicopter in front of you.

Long Rifle Mentioned: It wasn't tracking for me at first but I realized after you pick up your first kill streak you have to wait about 1min and 13seconds till a pop up on your screen says "press to use armament". After this I used the kill streaks and they tracked correctly.

Video guide:

MW3 - Helo Hat Trick
Destroy each objective helicopter in 'Reactor' with a different Armament

Mission Reactor
*note* this achievement is a bit buggy.
I used the Cruise Missile, Precision Airstrike & Mortar Strike to unlock this achievement. The stealth bomber & VTOL just missed the target completely.

I highly recommend watching my video below to see the locations of all the different armaments. This way if one armament doesn't work for you, then you can try a different one easily.

In the mission "Reactor" in the Modern Warfare III campaign, you are tasked with taking out 3 helicopters and each helicopter has a unique armament (killstreak) in the general vicinity.

Drop right into the first helicopter and land on the construction platform with supplies. To the left, there will be a self revive, ammo, SAM turret, and more but pick up the Mortar Strike and use it to target the first helicopter.

The second helicopter by the big warehouse with the letter "A" on it will have a precision airstrike at the base of the outside with various other supply materials. Pick up the airstrike and use it on the second helicopter.

Proceed to the roof next to the 3rd helicopter and either grab C4, Semetex/Frag or a RPG (location shown in video) and throw said explosive toward the 3rd helicopter. In the back of the roof, toward the dome is a Stealth Bomber. Use it on the 3rd helicopter for the achievement to pop!

** If the Stealth Bomber doesn't destroy the helicopter fully, there is a bomb drone in the back of the roof on a green crate. Use that to finish off the 3rd helicopter and the achievement will still pop!

The 3 armaments i can recommend are the bomb drone, mortar strike and precision airstrike as the Vtol doesn't tend to destroy in one go. Close to each of the helicopter sites you will find cargo that has been dropped with bright orange parachutes. The airstrke is easiest to find just north of the bottom helicopter near the main building. The mortar is just north of the western helicopter and the bomb drone is on the north side in the middle of the map by some transformers. The drone isnt enough so use one c4 to damage a helicopter first, Just be careful not to have the drone shot down. I intially used a vtol on one of the helicopters and had to finish with the bomb drone.