Re: Shouldn't the engines be more of a concern than the windows?
I don't believe that a drone is a practical weapon against a flying airliner, even one armed with explosive, just too difficult and risky to get it on target.
It would be so much easier to use a drone with a dangerous payload against a large public gathering, crowd such as a sports event. Two or three drones attacking in quick sequence could do some serious primary damage and as much trouble in the ensuing panic.
The risk to airliners from drones is mostly the possibility of accident.