Bomber Crew

For those who don't want to deal with getting this late, or risking experienced crew: This can be done the first mission on a new campaign.

Simply do one of the easier missions of the 3 starter missions, completing at least the main objective. ( supply drop was easy ).
Once you have met the main requirement, send your bomber back home.
Get close enough to tag the airbase for landing, but keep the landing gear up.
Once over your airbase, you are safe from any attacks, so start climbing to the highest altitude. The plane can still randomly break down though.
Send your 5 victims to sit on the wings outside the plane. Fast Forward time with LB, and you will circle the runway high up, and eventually they will die from exposure.
As soon as the 5th person keels over, send the plane to low altitude, and lower the landing gear. Barring no hydraulic/electrical failure, it should simply auto land and the achievement will pop after the debriefing screen.

EDIT: As APEX and SGT mentioned in the comments.... it helps odds of success if you buy the 2 survivors the thermal underwear set. The randomness of the game can have them dying due to cold/O2/breakdowns......

Of course, this is easier accomplished as you progress in the game and get skills like " emergency dive ", but since the nature of the achievement is killing off 5 crew, you might want to do it early on.

Start a new profile so you don't have to risk a crew you care about (also use it to work on the other negative achievements like losing engines and running fuel low).
Complete the rescue supply drop mission to get your pilot to level 2.
Next select the mission to bomb the ammo dumps.
[These can be interchanged but the sub mission is the longest of the beginning ones so avoid it]
Complete the objective then fly to mid altitude. Send all but navigator and pilot to the wings and perform an emergency dive with the pilot skill. They will fall off and you will be able to land with the 2 essentials.

*This worked better for me than the flying to high altitude and letting the crew freeze because at the very beginning you can't buy O2 canisters without 500 XP and I think this takes 2-3 missions to unlock. Also you don't have to spend any money or worry about malfunctions that may occur at high altitude... although they are also random I believe.
**it didn't pop until I went to the base overview and the profile saved, so you will lose those crew.