[ziddoap]

>Heathrow is a civilian airport, not a military one.

Not saying this incident is or isn't a national security issue, but this is not really pertinent to whether an incident is classified as a national security issue.

National security encompasses much more than just military-related stuff. The "security" part of "national security" is using a broad definition of security (like "food security" isn't strictly about physically protecting food from damage).