Most likely a 20 min wait at security. If you arent checking bags then 1.5 hours should be fine. Unless you are traveling with kids, in which case plan for 2 hours.
I agree with the rest that 2 hours minimum for Denver for memorial day weekend.
If you are using Frontier airline 2 hours is enough as there is no one working the desk till 2 hours before
Id be there 2 hours early, at a minimum. Its a fun airport with lots of opt for food and shopping. It won't be a chore 😉
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