[Mobhack]

1) LR sams have a very long minimum engagement range, usually. So they are usually ineffective against helos (unless you had a very wide map!). If so, then they will only be of use against bombers and fighter bombers etc.

2) If they have low skill chance (and Syrians are not very high experience), chances are they managed to fail thier skill rolls to fire on incoming planes, several times in a row, assuming you had several chances to fire.

3) If the EW difference roll between the incoming planes is high enough to reduce the shot to a very low probability, they may also not fire as it is not worth wasting a missile.

4) If supressed, they also may decide not to fire - but I'll assume they were not being bombarded?.

Cheers
Andy