The missile flew ten times higher than the worldwide space station and then back down to Earth.
The missile, which Pyongyang claims to be its "most powerful", crashed into the Sea of Japan.
While North Korea has claimed that their new weapon has put all parts of the United States within reach of a devastating strike, USA officials say the latest test was a failure since the missile broke apart on re-entry as the airliner witnessed.
In a message shared with staff, Cathay general manager Mark Hoey said the crew had described seeing the missile "blow up and fall apart", the South China Morning Post reported.
The AP reported the missile was in the air for almost an hour and reached an altitude of 2,780 miles before plummeting into the Sea of Japan about 600 miles from its launch point.
"Though the flight was far from the event location, the crew advised Japan ATC (air traffic control), according to procedure", the spokeswoman said, adding that flight operations had remained normal and was not affected, the Morning Post stated.
"At the moment, no one is changing any routes or operating parameters", Cathay said yesterday.
The Cathay Pacific flight took off from San Francisco and was bound for Hong Kong.
Given the arbitrary nature of the tests, it is possible that a North Korean missile could hit an airplane traveling through airspace near the launch site.
A Japanese daily reported Tuesday that Japan will overhaul its missile intercept system starting next year to cope with advancements in North Korea's weapons technology such as faster-descending missiles launched at steeper trajectories. In response to the test last week, Secretary of State Rex Tillerson called on China to do more to rein in North Korea, specifically through restraining the country's oil supply.
Pyongyang sent tensions soaring on the Korean Peninsula five days ago when it announced it had successfully test fired a new ICBM, which it says brings the whole of the continental United States within range.
"Singapore Airlines is aware of the reports on the sighting of the North Korean missiles and is closely monitoring the situation", a spokesperson said.
Regardless of whether or not the test failed on re-entry, the newest missile represents a technological breakthrough for the regime.