The new route avoided the northern part of the Sea of Japan, the spokesperson said.
Korean Air said the pilots on two of its flights bound for Seoul "saw a flash and everyone is assuming it should be the missile because of the timing".
The U.S. military reportedly detected preparations for North Korea's most recent missile launch at least 72 hours prior, according to The Diplomat, citing U.S. intelligence sources. However, it said it would not be changing any routes as a result of the incident.
A Japan Airlines spokesman told the BBC that as of Thursday, all routes were deemed "safe to operate", but they were "prepared to implement any route changes as needed".
North Korea tested its new Hwasong-15 (KN-22) intercontinental ballistic missile before dawn last Tuesday, but while the launch came as a surprise for many, the US intelligence saw it coming. "We remain alert and (will) review the situation as it evolves".
MEN: DARK PHOENIX Plot Explained
X-Men: Dark Phoenix , the next installment in Fox's mutant shared universe, is hitting theaters in a little less than a year. We'll be on the lookout for more clues as we get closer to the release of X-Men: Dark Phoenix on November 2, 2018 .
The ICBM was sacked on a lofted trajectory rather than a minimum energy trajectory, putting more structural stress on the missile's re-entry vehicle but reducing the duration and intensity of temperature-based stresses.
In August, Air France-KLM expanded its no-fly zone around North Korea after a missile test.
Meanwhile, tensions on the Korean Peninsula continue to escalate, with the US and South Korea launching major joint drills on Monday. Pyongyang has said the drills prove that US President Donald Trump is "begging" for nuclear war.
But the United States, with a network of satellites, drones, and spy planes frequently patrolling the skies above North Korea, spotted the test anyway.
Russian Federation and China have also called on a halt in the joint exercises as part of a so-called "double freeze" plan. However, the proposal was swiftly rejected by Washington over the summer.