Local
Flights that landed at the border due to technical problems were canceled shortly after

DENVER (KDVR) – All Frontier Airlines flights are grounded due to automation issues, according to Federal Aviation Administration. The Air Traffic Control Systems Command Center canceled the ground stop after 10 a.m. MDT.
Since Frontier is based in Denver, all grounded flights can cause problems at Denver International Airport and around the country during the morning and possibly throughout the day.
Estimated times are not provided for dwell times or details of technical issues.
This is a groundbreaking story. Check again for updates.
https://kdvr.com/news/local/frontier-flights-grounded-due-to-technical-issues/ Flights that landed at the border due to technical problems were canceled shortly after