Route reliability record
ORD→DEN
Chicago to Denver
- Flights
- 6,118
- Period
- September 2025 to August 2026
- Distance
- 888 mi
- Carriers
- 5
This route sits in the middle of the pack with a C. Close to three flights in four arrive on time by the DOT's definition, 3 points worse than the national rate of 77.3%. The late ones land a little over an hour behind schedule. That rests on 6,118 ORD to DEN flights, of which United Airlines flew 3,888 at 78.3% on time.
Best time to fly ORD to DEN: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 89.9% of the time and Saturday flights 79.7%, against 74.3% for the route overall.
The US average over the same twelve months is 77.3%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
74.3%
Arrivals under 15 minutes late, of 6,029 completed flights
Avg delay
78 min
Across delayed arrivals only, not all flights
Cancelled
1.19%
National rate is 1.89%
Best carrier
United
78.3% on time across 3,888 flights
These figures cover 6,118 flights between September 2025 and August 2026. Beyond the headline rate, 10.4% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Which airline is most reliable on ORD to DEN
The choice of carrier is not cosmetic here. United Airlines arrives on time 78.3% of the time; American Airlines manages 65.5%. Sample sizes sit next to every figure, because a two-point gap across 1,475 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 3,888 | 78.3% | 76 min | 0.87% | B+ |
| Envoy Airthin sample | 129 | 76.7% | 52 min | 0.00% | B+ |
| Southwest Airlinesthin sample | 302 | 74.4% | 72 min | 1.66% | C |
| Frontier Airlinesthin sample | 324 | 66.0% | 123 min | 3.40% | C− |
| American Airlines | 1,475 | 65.5% | 73 min | 1.56% | C |
The spread between United and American is 13 points, wide enough that it should decide the booking. On a hundred trips that is 13 more arrivals inside the on-time window.
Flight by flight
Flights on ORD to DEN
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Best ways to make this trip
The most reliable ways to fly Chicago to Denver
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 1 of the top 3 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. ORD → DENChicago to Denver | United Airlines | 77.6% | 78.3% | 0.87% | 5am–8am, Sat | UA 1803 10:40 |
| 2. MDW → DENChicago to Denver | Southwest Airlines | 71.9% | 72.9% | 1.32% | 5am–8am, Tue (route) | — |
| 3. ORD → DENChicago to Denver | American Airlines | 64.5% | 65.5% | 1.56% | 5am–8am, Tue | AA 1387 20:45 |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 28 points, against 13 points between the best and worst carrier.
- 5am–8am1,027 flights89.9%
- 8am–11am987 flights77.8%
- 11am–2pm947 flights81.7%
- 2pm–5pm1,435 flights69.9%
- 5pm–8pm583 flights62.0%
- 8pm–5am1,139 flights62.8%
Scale runs 55% to 95%.
The 5pm–8pm window is where this operation falls apart: 62.0% on time, against 89.9% for the 5am–8am 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 2pm–5pm window is the busiest, with 1,435 flights scheduled in it.
Explore
Filter ORD to DEN by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On ORD to DEN, the best departure window is 5am–8am at 89.9% on time and the worst is 5pm–8pm at 62.0%, a wide gap of 27.9 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am89.9%
- 8–11am77.8%
- 11am–2pm81.7%
- 2–5pm69.9%
- 5–8pm62.0%
- 8pm–5am62.8%
best all US flightsScale 55% to 95%.
Across the year
When delays peak on this route
This route's year swings by 15 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
August is the worst month at 65.0% on time, 15 points below September, the best at 80.4%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. October was the busiest month here, with 616 flights.
Across the week, Saturday is the strongest day at 79.7% on time and Monday the weakest at 71.0%, a spread of 9 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 46% of the 120,000 delay minutes carriers reported here, and the remaining four split what is left.
- 46%Late-arriving aircraft
- 26%Carrier
- 23%National Airspace System
- 5%Extreme weather
- 0%Security
46% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 120,000 reported delay minutes here, that single category outweighs weather by 10 to one. The split is drawn from 120,243 reported delay minutes.
The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 89.9% on time here.
Cancellations sit at 1.19% against a national 1.89%, which is ordinary. Diversions add another 0.26%.
Connections and stage length
What a delay here actually costs
10.4% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection 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.
The return leg runs 71.8% on time across 6,109 flights, within 3 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 6,118 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
Work out the risk of missing a connection in DEN after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 80.4% on time and August 65.0%, a swing of 15 points. If the dates move at all, move them out of August before you think about anything else. 6,029 completed flights over 12 months sit behind that.
Common questions
ORD to DEN questions
How often is ORD to DEN delayed?
About one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 25.7% of the 6,118 flights in this analysis, against 22.7% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on ORD to DEN?
United Airlines leads at 78.3% on time across 3,888 flights. American Airlines is at the other end on 65.5%, a gap of 13 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on ORD to DEN?
The 5am–8am departure window is the strongest at 89.9% on time. The 5pm–8pm window is the weakest at 62.0%, 28 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are August delays on ORD to DEN?
August is the weakest month at 65.0% on time, compared with 80.4% in September. Across the year that is 15 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- DEN to ORD — the return legseparate record
- Chicago O'Hare International (ORD) delay statistics
- Denver International (DEN) delay statistics
- United Airlines on ORD to DEN78.3%
- Envoy Air on ORD to DEN76.7%
- Southwest Airlines on ORD to DEN74.4%
- Frontier Airlines on ORD to DEN66.0%
- American Airlines on ORD to DEN65.5%
- ORD to LGA, a related route66.6%
- PHX to DEN, a related route76.7%
- ORD to BOS, a related route66.6%
- United Airlines on-time record78.3%
- Envoy Air on-time record76.7%
- Southwest Airlines on-time record74.4%
- Same route, different airline: where the carrier you pick matters most
- Why the first flight of the morning is statistically safest
Direction matters. ORD to DEN and DEN to ORD are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.