As best I can tell, Syria has about 300 combat fixed-wing aircraft. Why not destroy all of them? Planes spend most of their time on the ground. They can be destroyed by a .50 cal. sniper rifle fired from about 1,000 meters away. Land a remote-operated belt fed .50 cal. on top of a building or on a hill at night. Put an incendiary or exploding bullet into every plane at that base. Cost? I would guess $500 or so.
Or deliver small thermite grenades to the wings of them by small helicopter drones. Cost? Probably about a $1,000 before they started preventing such attacks.
After initial success, Syria would start putting shotgun-armed guard to shoot the drones. So accompany the infrastructure-destroying drones with guard drones that kill guards. Guarding against the sniper rifles firing from 1,000 yards is much harder to do.
Syrian jets are also relatively easy to shoot down and kill the pilot if you hit them when they are landing or taking off. when they are low to the ground an ejecting pilot is too low to survive. How do that?
60 Minutes did a segment about the ability of the US to send swarms of small drone aircraft after a target. So give Syrian jet that are taking off or landing a drone version of the geese that brought down Sully Sullenberger’s airliner. I don’t think you need a swarm. Flying just one drone into the engine of a Syrian jet probably kills it. When taking off and landing, jets have limited speed and ability to evade the attacker.
Drones can also fire while flying. I do not know how much accuracy they lose because of motion and vibration.
My main point is for all their mighty capabilities at full speed flight, Russian jets that have been sold to Syria spend most of their time sitting motionless on the ground and they are even extremely vulnerable when landing or taking off.
We don’t need $1.41 million cruise missiles to deal with these guys.