We have seen the ability of Russian Air Defence systems in case of Iraq and Libya. However it was US who was taking them out that time but Turkey also has a very good airforce with large fleet of F-16s plus advance EW system and Syria is not a match for it. First of all the defections are from all branches of the Syrian armed forces and it has affected their operation ability a lot. In case of Syrian Airforce it can not face much superior Turkish Airforce. Moreover most of the Pilots are Sunnis even if they are still serving it will be a great risk for Assad regime to use them or they will defect with their aircrafts. Its a right time that US, NATO and GCC plus Arab nations supportiing syrian peoples revolution must intervene militarily and the brutal killer regime will crumble in days. Example is HOMS city. Despite the relentless n continuous bombing of this besieged city they havent succeded in breaking the will of few hundred ill equipped FSA fighters. I think Insha Allah world is going to see an amazing victory of blood over the guns and tanks.