According to an October 1, 2007 Fact Sheet, the FAA is starting to use the International Civil Aviation Organization (“ICAO”) definition of runway incursion. Prior to adopting the ICAO definition, the FAA defined an incident without an aircraft in potential conflict (e.g. an unauthorized aircraft crossing an empty runway) as a “surface incident” and not a runway incursion. Now, any unauthorized intrusion onto a runway, regardless of whether or not an aircraft presents a potential conflict, will be considered a “runway incursion.”
According to the Fact Sheet, “[t]he FAA is making the change so the worldwide aviation community will have a single runway incursion definition, which in turn could help in the search to determine common factors that contribute to these incidents.” Interestingly, the FAA helped ICAO come up with its definition of “runway incursion,” which was adopted in November 2005.
I don’t think this change means a lot for airmen, at least not in the enforcement context. Whether an event is “classified” as a “surface incident” or a “runway incursion,” the FAA will likely still pursue enforcement for the associated operational violation(s).