My question is why this would necessitate the shutting down of the runway if the incursion took place on a taxiway? Mark Tokyo's Narita Airport had to close one of its two runways for nearly an hour on Wednesday after an incoming plane ended up facing an outgoing aircraft on the taxiway, airport officials said. The two planes -- a KLM Royal Dutch Airlines passenger aircraft arriving from Amsterdam and a South Korean Asiana Airlines plane preparing to depart for Incheon -- were taxiing towards each other, the officials said. They did not collide. The runway at Japan's main international air hub just north of Tokyo was closed for about an hour while workers removed the planes, they said. "We still don't know why it happened. Investigations are under way," one of the officials said.