Here is some information from fly Denver's website on their checkpoint security. Terminal North TSA checkpoint - 4 a.m.-ish to approx. 9 p.m. Terminal South TSA checkpoint - open 24 hours a day A Bridge TSA checkpoint - 4:30 a.m.-ish to approx. 6 p.m.
The main security never closes as long as you have flights in and out of DIA.
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