If your goal is just to kill as many people as possible (rather than, e.g., needing the plane for smuggling or hijacking), surely there are enough events where

If your goal is just to kill as many people as possible (rather than, e.g., needing the plane for smuggling or hijacking), surely there are enough events where people are packed together that it could be done with or without TSA lines? Take any music event for instance - the standing area will be packed, and security will be minimal if any (last time I went to Wembley Arena the bag search was pointless - I had a jacket in mine that completely obscured the bag contents, and there could easily have been an explosive device concealed below. FWIW, this was only a few months after the Bataclan attack, and the venue had specifically said to arrive early due to increased security). The security lines are definitely a softer target than needing to get on the plane, but soft targets are easy to find anyway.