Northern Ireland: "Welcome to hell, lads!"
Does the GTD include incidents of state terrorism?
No, the GTD is limited to acts of non-state terrorism. One of the three necessary criteria for inclusion is that there must be sub-national perpetrators.
https://www.start.umd.edu/gtd-faqs#q3
I would assume this is why, as the prevailing theory is Lockerbie was sponsored by Libya
Wikipedia suggests the database isn't particularly academically sound either.