 For Rocky Mountain News Network, I'm Teresa Taylor. Frontier Airlines passengers were stranded at airports across the country, including Denver International Airport, due to a computer problem that put the airline on a nationwide ground stop. Frontier posted on social media just after 6 p.m. that their systems were impacted by a Microsoft outage. At around 8.45 last night, the spokesperson said the ground stop had been lifted and that they were in the process of resuming flight operations.