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.