Michael Edward Applegate, 43, from Seattle and arrived with his family at Narita International Airport on Monday, according to the airport police. He was planning to transfer to a domestic flight to Okinawa where he was due to start a new job as a firefighter for the United States Navy.
But when he arrived in Narita – around 70 kilometers (43 miles) from Tokyo – – airport authorities found he had a Smith & Wesson automatic handgun loaded with 14 bullets, and a magazine loaded with another 14 bullets in his checked luggage.
Applegate confirmed to airport police that the gun was his own, but he said he didn I know why it was there ̵
The 43-year-old is a custody at the Narita International Airport police station, although he has not been charged with violating Japan's swords and firearms control law, which imposes on almost blank ban on citizens owning firearms.
If he's charged and found guilty, he faces a minimum of three years and a maximum of 20 years in jail.
Under Japanese law, guns and bullets must be stored separately.
CNN has reached out to the United States Transportation Security Administration (TSA) for comment.
At the time, Japan's Transportation Ministry said there would be no penalties for Delta Air Lines or the TSA. But it did TSA responsible and asked the organization to take preventative measures.