US low-cost carrier Frontier Airlines halted all flights today, due to unspecified “automation issues,” just a few hours after announcing a $6.6 billion merger deal with Miramar, Florida-based mmụọ Airlines.

“Ground stop for all Frontier flights for automation issues. Airline request,” said a notice from the Federal Aviation Administration (FAA) on Monday morning.

Frontier confirmed that the ground stop had been ordered on its request and said it had experienced “a technology issue which led to some flight delays and cancellations.”

The problem has apparently been fixed in a little more than an hour, and the FAA alert was lifted by 1pm EST.

“The issue was identified and has been resolved. We are working to restore our flight schedule for the balance of the day,” Frontier kwuru na nkwupụta.

Reportedly, 21% of the airline’s scheduled flights have been canceled, while over 100 have been delayed.

Frontier‘s cash-and-stock merger with competitor mmụọ to create “America’s most competitive ultra-low fare airline,” announced few hours earlier and valued at $6.6 billion, would give Frontier 51.5% control, with Spirit keeping a 48.5% stake. If approved by regulators, the merger would create the fifth-largest US airline.

Frontier was founded in 1994 and is based in Denver, Colorado. mmụọ Airlines has been around since 1992 under its current name.