Delta has lifted its groundstop and is allowing limited departures, officials said on Twitter.
"Customers headed to airports should expect delays/cancellations," Delta said on Twitter.
The airline has canceled approx. 427 flights, but is operating more than 1,590 flights, as of 11 a.m. MT, according to Delta.
The problems started after a power outage in Atlanta at 12:30 a.m. MT impacted Delta's computer systems worldwide.
Flights that were already in the air when the outage struck continued, but many flights remained grounded. Over the next several hours, only a handful of flights took off instead of the usual hundreds, according to flight-tracking services.
At DIA, passengers were able to use computers to check in starting around 5 a.m.
Delta has 39 departures and 29 arrivals at Denver International Airport scheduled for Monday. The flights were listed as on time on DIA's website. However, airport officials are suggesting that passengers check with Delta for updates.