Updated

The midrange ballistic missile that was fired over Japan by North Korea was done so under what appear to be new methods by the Hermit Kingdom.

Tuesday’s launch was the first-ever reported from Sunan, which is home to Pyongyang's international airport. Some outside observers wondered if North Korea had launched a road-mobile missile from an airport runway — something South Korea's military couldn't immediately determine.

The airport's runways could provide the ideal space to launch a road-mobile missile like the Hwasong-12, while also demonstrating that the North can launch its missiles from anywhere, according to Moon Seong Mook, a former South Korean military official and current analyst for the Seoul-based Korea Research Institute for National Strategy.

North Korea will no doubt be watching the world's reaction to see if it can use Tuesday's flight over Japan as a precedent for future launches.

Any new test worries Washington and its allies because it presumably puts the North a step closer toward its goal of an arsenal of nuclear missiles that can reliably target the United States. Tuesday's test, however, looks especially aggressive to Washington, Seoul and Tokyo.

The North has conducted launches at an unusually fast pace this year — 13 times, Seoul says — and some analysts believe Pyongyang could have viable long-range nuclear missiles before the end of President Donald Trump's first term in early 2021.

The North's launch over Japan shouldn't be a total surprise. Earlier this month, when threatening to lob four Hwasong-12s into the waters near Guam, North Korea specifically said they would fly over Japanese territory.

North Korea in June also angrily reacted to the launch of a Japanese satellite it said was aimed at spying on the North and said Tokyo was no longer entitled to fault Pyongyang "no matter what it launches or whether that crosses the sky above Japan."

The Associated Press contributed to this story.