Carrier route record

F9ORD→DEN

Frontier Airlines · Chicago to Denver

Flights: 332
Period: July 2025 to June 2026
Share of route: 5%
Carriers: 5

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Frontier Airlines.

Frontier on ORD to DEN sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 5 points worse than the national rate of 77.6%. The late ones land about 2.3 hours behind schedule. That rests on 332 flights. The strongest carrier on the route with a full sample, United Airlines, flew 3,758 at 77.4% on time.

United Airlines is the most reliable of the three carriers covered here at 77.4% on time across 3,758 flights.

On time

72.5%

Arrivals under 15 minutes late, of 324 completed flights

Avg delay

139 min

Across delayed arrivals only, not all flights

Cancelled

2.11%

National rate is 1.81%

Whole route

74.2%

Every carrier on ORD to DEN, 6,169 flights

These figures cover 332 flights between July 2025 and June 2026. Beyond the headline rate, 14.2% of arrivals land a full hour or more behind schedule. That is the number that wrecks a connection, and it is not visible in an on-time percentage alone.

Carrier by carrier

Frontier against every carrier on ORD to DEN

Frontier flew 332 of the 6,169 flights on ORD to DEN, about 5% of it. Its 72.5% on time is 2 points worse than the route as a whole, which runs 74.2%. Ranked by on-time rate it is number four of five carriers on the route, where the range runs from United at 77.4% to American at 66.5%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.

The choice of carrier is not cosmetic here. United Airlines arrives on time 77.4% of the time; American Airlines manages 66.5%. Sample sizes sit next to every figure, because a two-point gap across 1,471 flights means less than a ten-point one.

On-time performance by carrier on ORD to DEN
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	3,758	77.4%	73 min	0.93%	B+
Envoy Airthin sample	125	76.0%	52 min	0.00%	B+
Southwest Airlines	483	73.0%	68 min	1.66%	C
Frontier Airlines (this page)thin sample	332	72.5%	139 min	2.11%	C
American Airlines	1,471	66.5%	76 min	1.77%	C

United leads American by 11 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.

Flight by flight

Frontier flight numbers on ORD to DEN

F9 148307:0072.3% · 281 flights

Departure window

When Frontier runs best on this route

Departure time matters more here than the choice of carrier. The gap between the best and worst window is 23 points, against 11 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am171 flights75.3%
8am–11am27 flights—
11am–2pm32 flights81.2%
2pm–5pm19 flights—
5pm–8pm23 flights—
8pm–5am60 flights58.6%

Scale runs 50% to 85%. Rows with fewer than 30 flights show a dash.

The 8pm–5am window is where this operation falls apart: 58.6% on time, against 81.2% for the 11am–2pm slot. By evening the aircraft flying these rotations have absorbed a full day of small delays and there is no slack left to recover in. The 5am–8am window is the busiest, with 171 flights scheduled in it.

Across the year

Frontier on ORD to DEN through the year

Jul–Sep 2025116 flights79.1%
Oct–Dec 202596 flights69.6%
Jan–Mar 202650 flights75.5%
Apr–Jun 202670 flights63.2%

Scale runs 55% to 85%. Rows with fewer than 30 flights show a dash.

Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 72.5% on time across 332 flights.

Frontier on ORD to DEN did not run the same all year. Its best quarter was Jul–Sep 2025 at 79.1% on time and its weakest Apr–Jun 2026 at 63.2%, a swing of 16 points on roughly 83 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.

Across the week, Friday is the strongest day at 78.9% on time and Saturday the weakest at 64.9%. 14 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Frontier runs late on this route

One category carries most of the weight here. Late-arriving aircraft accounts for 53% of the 12,000 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.

Late-arriving aircraft
53%
Carrier
32%
National Airspace System
9%
Extreme weather
6%

53% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. That is a cascade, and cascades start small and grow through the day. Across 12,000 reported delay minutes here, that single category outweighs weather by 9 to one. It is the strongest argument for booking the first departure of the morning, when the aircraft has been sitting at the gate overnight with nothing to inherit. The split is drawn from 12,409 reported delay minutes.

Cancellations sit at 2.11% against a national 1.81%, which is ordinary. Diversions add another 0.30%.

Connections and stage length

What a delay here costs

For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 14.2% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.

The 888 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.

The return leg is a different operation and performs like one: it runs 68.6% on time across 329 flights, 4 points below this direction. Departure banks, aircraft rotations and the congestion at each end all differ, so scoring the two directions together would average away a real 4 points of difference.

One caution: this is a thin sample. 332 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.

What to do with this

Booking Frontier on ORD to DEN

Put together: treat all of this as provisional. 332 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 72.5% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 324 completed flights over 12 months sit behind that.

Where to go next

Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.

Key figures