I think 2. can be ruled out. It’s hard to imagine a terrorist group doing this considering the risk of getting caught. Much easier just to drive a truck into a crowd or something.
A swarm of two dozen drones costing less than $50k could foul all of a passenger airplane's engines within a few thousand feet of takeoff. The evidence would be pretty junked up and there is no easy way to trace it back to the controller while it's happening. No sacrificial terrorist cell member needed.