I realize this is hard to analyze since it depends heavily on the type of missile and also the fact that there’s been relatively little air combat in the modern post-Vietnam age. But how often does an airplane spitting out chaff and flares actually work to spoof away an incoming missile? (without use of other ECM)
30 percent, 50 percent?
I’m sure it depends on who the adversary is. Are we talking an adversary with US-level tech, or some two-bit nation that’s still maintaining a stockpile of 1970-era heat-seekers? As long as the low-tech nations represent a significant fraction of the likely plausible enemies, keeping around countermeasures that will fool them sounds worthwhile.
The answer to this depends heavily on the missile in question, distance, and a host of other factors. Very early missiles (Falcon, early Sidewinder)would probably be defeated just with flares but anything built since the eighties require a combination manuevers, EA (ECM), and flares/chaff. If you’re talking Gen4/5 aircraft and AA missiles then all three have to be used in order to survive an encounter.