The other hint is the timing

> On October 16, 2019, FedEx applied for a supplemental type certificate to install a laser-based missile-defense system

This was the only airliner shot down in the 10 years prior, it has to be the incident that inspired this.

https://en.wikipedia.org/wiki/List_of_airliner_shootdown_inc...

That wasn't shot down with IR manpads though. The likely suspect is a vehicle mounted radar based system.

Most manpads don't pose a threat at reasonable cruise altitude. They're more of a takeoff/landing threat. There's a minimum warhead size to do the job and a minimum fuel required to get it to a given altitude. Anything that can reach an airliner at a typical cruising altitude is going to be vehicle mounted for the foreseeable future.