There are plenty of 'known terrorists.' That's a silly argument. I used to hunt and find these guys in some secret squirrel units with the Air Force. The list of possible targets is lengthy and they aren't on that list for flimsy reasons generally. That being said, in my experience, this would only be for early use as a development target and is not 'actionable' intelligence; it wouldn't get you on the "things to do" list. It's the kind of intel that, if one of these guys went and pulled off a suicide bombing, would be used to say that he was already labeled a terrorist and should have been taken out despite not really having much to go on other than being on a computer generated list in a pile of thousands. There aren't enough resources in the first place to be making any use of this information other than feeding it into another system which either verifies it and builds a case, or rejects it. And likely that system is human, labor intensive, and overworked. Big data that is this inefficient does not translate into big results.
In reality, the high amount of civilians being killed by drone strikes are a real consequence of drone warfare meeting guerilla warfare. When combined with the USAF stance that anyone who is a military aged male (MAM) associating with known terrorists is not a civilian and is not considered collateral damage, and how that definition does not always carry with other non-military agencies, you can see how the civilian count is so high when not disclosed by the US government.
When people ask why I don't want being on the no-fly list to preclude second amendment rights this would be a good reason. The no-fly list is non-judicial and has no threshold for inclusion which is possible to appeal or even petition to understand. And yet, getting put on this suspected terrorist list, would be a very obvious step to getting put on the no-fly list.