Board Thread:General Discussion/@comment-775697-20150128051757/@comment-25467429-20150220132623

The system is really not all that complicated. There is a preset number of items that will receive research at the end of a mission, 2-4 depending on fuel used and if one is the winner or not. If you use stocked fuel, research is guranteed on the plane you used that mission, unless its research is already maxed out (you haven't bought into the next level, or you have literally maxed out its level). From there it randomly selects from the available to research items you have either on the aircraft/parts tree or the special weapons tree. If you have more items available to reserach than the 2-4 lottery chances, some part isn't going to get research. If you have less, then all the items available for research will get their research, and you get a "refund" of in-game credits for not conducting any research.

How much progress each item gets is also a bit random, but within a narrow range. That is more based on the internal PA decision on what planes and parts deserve faster research at what stage. A low-tier plane, even before the last update, usually progressed much faster in terms of how much reserach was done in one shot. The example of the F-117A above wasn't unusual before either. Even now, I personally had that kind of growth on the FALKEN after I first started reserach on it - just one-shot it went up around 40% after a mission. But aftewards, reserach slows dramatically as a plane is either high-tier or high level, or both. I think for the most part, I can't confirm, SP planes and other high-tier aircraft generally settle into a narrow range of ~2% to 5% growth at every reaserch opportunity, thus take longer to develop than say the F-117A which, based on similar tier planes, will have research advance at anywhere from 2% to 40%+. For these planes, that sort of research growth seems to be handled much like the crate prize drops at the end of the mission - sometimes you'll get something good, or sometimes you'll just get a Supply Ticket.

Also, keep in mind Forced Sorties do play a role as well. I'm not sure of the multiplier, but they at least treat it as equivalent to the number of units of fuel you used - 2.1x the reserach advance for 2 units of fuel, 3.5x for 3.