This issue was reported earlier but misinterpreted by a dev and marked as resolved. 12106
Please bring back semiautomatic flare mode for all air vehicles. The ability to pop a single pair of flares after a gun run, etc would be required in the event that properly simulated Passive-IR guided missiles from MANPADS or aircraft were implemented.
It is also far better to allow the pilot to decide how many flares he's going to pop, whether it'll be less (more risky but conserves flares) or more (safer, run out of flares faster).
Semi-auto flares were the default in Arma II, and it should be that way in Arma III as well.