It looks like the girls of NewJeans were caught up in the chaos caused by the Federal Aviation Administration outage on the morning of January 11, leaving them stranded in the U.S. for a day. 

On January 12, ADOR announced the cancellation of all of NewJeans's schedules for Friday, January 13. The agency stated,

"We would like to notify you with an update regarding NewJeans's schedule.

NewJeans planned on returning to Korea after completing their overseas schedules today, but a data processing system malfunction in the U.S led to the mass cancellations and/or delays of flights across the country. As a result, the members are currently unable to return to Korea as planned.

Thus, NewJeans will not be able to attend their schedules originally planned for January 13 including KBS's 'Music Bank' as well as their fan sign event. The announcement of winners for the 'Music Bank' pre-recording audience draw, which was scheduled for January 12 at 12 PM KST, has also been cancelled. We will notify you with additional details regarding the rescheduling of the fan sign event through the album distributor. 

Although we searched for domestic substitute flights which would allow NewJeans to participate in their schedules as much as possible, the aftermath of the chaos caused at domestic airports was too great, and unfortunately, it has become difficult for the group to fulfill their schedules as planned.

We ask all fans who waited eagerly for NewJeans's stage on the January 13 broadcast of 'Music Bank', as well as for the fan sign event, for their generous understanding.

We will do our best to ensure that the members of NewJeans return to Korea safely."

Earlier on the morning of January 11, a "computer glitch at the Federal Aviation Administration delayed airline traffic across much of the nation", according to U.S. media outlet reports. Approximately 10,000 flights across the U.S. were delayed temporarily, with over 1,300 flights being cancelled.