20 years ago, I was an avionics technician on F-16 fighter jets in the USAF. We had 'FOD Walks' daily, which involved slowly walking down the flightline while staring at the ground, and picking up any loose objects
Even a tiny object, when ingested into a jet engine, can cause catastrophic damage. And F-16s have intakes very low to the ground, making them a much higher FOD risk.
The worst FOD events were when something broke. We used bit drivers to remove aircraft panels, and the bits were fairly standard screwdriver bits. Sometimes, one of those bits would shatter when applying force to remove a stubborn fastener. If that happens, you have to retrieve every single piece of metal. If you return your toolbox at the end of the day and it is missing anything that can't be accounted for, the entire flightline could be shut down while a search is carried out.
Dropping things in the cockpit could sometimes be much worse. If it drops down into a void left by removing a control panel, then it could potentially fall to the 'bottom' of the aircraft. If that happens, you'll be taking off all the panels in that vicinity, you'll have multiple people looking with flashlights, borescopes, etc.
If something is dropped but can't be found, that's probably a multi-day event that will involve some fairly high ranking people.
FOD was considered a serious threat, and a tiny piece of metal broken off of a tool could hinder operations for days at a time
