Cold Alley

Just wanted to add something to the other solution posted here.

I've been playing the same mission to get 10,000 kills - Number 2 - the helicopter mission. However, I noticed that the cutscenes take forever, even with holding down the fast-forward button. I found a sweet spot where you can kill a bunch of enemies, exit out of the level, and resume at the last checkpoint you had. I was getting 12 or 13 kills in about 15 seconds, which is about 50 per minute, and cuts the completion time to about 4-6 hours (3-5 just grinding kills). I have two options that I used to grind out these fast kills:

1) So load up mission 2, the helicopter mission, and proceed through the level until you kill the truck on the bridge (the one that shoots a missile at you). From there you can quit out and resume the mission at the last checkpoint. You'll start right by the bridge again (no cutscenes!!) and you can kill the 12 vehicles (not sure if shooting the missile counts as a kill). Rinse and repeat.

2) You could also let the game proceed a little further, because there's another big cluster of enemies right after the next short cutscene. You'll enter a beach/dock area, then a village, and proceed up a road killing enemies along the way. Finally there's a small group of 3 enemy vehicles. Once you kill those you can quit out again and resume right at the bridge. If you go any further you'll have another long cutscene (a bombing run) and a new checkpoint, and only a trickle of enemies that are harder to shoot. So quit out after you shoot the small group of three enemies.

I would use option 1 when I was paying attention and really focusing on grinding. That usually didn't last long, because grinding this way, while fast, is an utter bore. I used option 2 when I was trying to multitask and keep myself from falling asleep. The short cutscene after killing all the enemies by the bridge allowed for a brief moment of respite which allowed me to do something else for 15-20 seconds. I would either be watching a movie, doing a chore, or grinding out achievements in another game.

Anyways, I found this method to really save some time. Instead of getting 100-150 in 6-7 minutes I was getting about 50 in 1 minute. Hope that helps!

Edit: After getting 5,000 kills my progress towards 10,000 kills was suddenly reset. Therefore, if possible, I'd recommend trying to get all 10,000 kills in one sitting. I'm also going to try setting up some type of macro to see if I can automate this gruesome process.

Get ready for a little bit of a grind folks, 10,000 kills in an aerial combat game does seem a bit daunting, but I'm going to try and ease the pain a bit. First off is the most obvious, play through the campaign first, it should give you a decent amount of kills, but nowhere near 10,000. Now the easiest way to get kills that I found was to keep playing over & over the second mission: The Helicopter War. You don't even pilot a aircraft, you are merely a chopper gunner for the duration of this mission and every orange marker on the ground you kill counts as one towards your total kills. There are a little over a hundred enemies in this mission, and it's rather short too. I hope this helps everyone out as this is quickest way I could think of doing this in this game.

For the people not feeling like grinding this, I used tinytask for this on the checkpoint mentioned by Xtowers. Wish Id done that sooner as I did the first 6k legit but idling it is much easier.