You arrange a weight to fall on a control cable. Loosen the cable guide. Time delay, spring, etc. It overwhelmed the ability of the stick to pushback. And when the wreckage is collected, it's just another object with no connection to anything. No explosive residue, no timer, red and green wires to cut…nothing.
Software implants are becoming possible for the larger executive jets. Like Toyota crash-by-wire cars.
Want to "send a message"? Use something that can be found. Polonium, poisons, etc. then they know.
7/10? Do a statistical analysis of the last 4 months vs last 4 years, vs. last 40 years.
The last couple of months is a hockey stick, a real one.