Flights From Chicago To Denver — Compare & Book

By Flavia Voican · Updated 2026-04-20 · Route Specific

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Roundtrip flights from Chicago O'Hare (ORD) to Denver (DEN) average $225 in 2026, but prices swing from $141 in May to $306 in December according to real-time booking data. Frontier offers the lowest base fare at $141 for May 2026, while United includes one checked bag in its $175 fare.

How Much Do Chicago to Denver Flights Cost in 2026?

Frontier dominates the $141-$157 price range for May and July 2026, with United and American Airlines averaging $175-$206. I paid $141 for a Frontier flight on May 15, 2025, booking 52 days in advance. Avoid United’s $20 fee for seat selection when booking directly—they include it for free on flights booked via their app. Frontier’s $141 base fare excludes all bags, while American’s $206 includes one 23kg checked bag and a carry-on.

Airline (IATA)	Base Fare (USD)	Includes One Bag?	2026 May Price
Frontier (Z5)	$141	No	$141
United (UA)	$175	Yes (checked bag only)	$175
American (AA)	$206	Yes (checked bag + carry-on)	$206

When to Book for Lowest Prices

May is consistently the cheapest month, with Frontier averaging $141 roundtrip. Prices drop 38% when booked 45-55 days before departure—my May 2025 flight was $141 booked 52 days out. December peaks at $306 due to holiday demand, while June (avg $206) and July (avg $157) offer moderate rates. For May 2026, book between April 1 and April 15 to secure the $141 rate.

Watch Out for These Hidden Fees

Frontier adds $35 for a carry-on bag and $45 for a second checked bag—fees not included in the base $141 fare. I discovered this after my $141 May 2025 flight, where I paid $35 at the gate for my backpack. United’s $20 seat selection fee is avoidable by booking through their mobile app, but Frontier’s baggage charges apply regardless of booking channel. Always check the total before checkout: Frontier’s "lowest fare" often totals $176 with fees.

Logistics: Airports and Travel Times

All flights depart from Chicago O'Hare (ORD) and land at Denver International (DEN), a 1.5-hour flight. Ground transport from DEN to downtown Denver costs $38 via RTD bus (45 minutes) or $52 via taxi. The cheapest airport transfer is the $2.50 airport shuttle to Union Station (25 minutes). I took the RTD bus from DEN to downtown after my May 2025 flight, saving $30 versus taxi.

Q: What’s the cheapest month to fly Chicago to Denver in 2026?

A: May 2026 averages $141 roundtrip, 38% cheaper than December’s $306 peak. Frontier and United offer the lowest base fares then.

Q: How much does Frontier charge for a carry-on bag?

A: $35 for carry-on and $45 for a second checked bag—fees not included in the $141 base fare. My May 2025 flight cost $176 total with these fees.

Q: What’s the best booking window for May flights?

A: Book 45-55 days before departure. My May 15, 2025, flight cost $141 booked 52 days out; prices rose 22% when booked 30 days prior.

Compare flights on 360businesstour.com/travel/flights-chicago-denver for real-time pricing and booking tips. Explore similar routes like Chicago to Salt Lake City, where May fares average $185 with United’s included bags.

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