Route reliability record
ORD→DEN
Chicago to Denver
- Flights
- 6,198
- Period
- June 2025 to May 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 77.4%. The late ones land a little over an hour behind schedule. That rests on 6,198 flights, of which United Airlines flew 3,701 at 77.6% on time.
United Airlines is the most reliable of the three carriers covered here at 77.6% on time across 3,701 flights.
Key figures
On time
74.1%
Arrivals under 15 minutes late, of 6,109 completed flights
Avg delay
77 min
Across delayed arrivals only, not all flights
Cancelled
1.16%
National rate is 1.80%
Best carrier
United
77.6% on time across 3,701 flights
These figures cover 6,198 flights between June 2025 and May 2026. Beyond the headline rate, 10.1% 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
Which airline is most reliable on ORD to DEN
The choice of carrier is not cosmetic here. United Airlines arrives on time 77.6% of the time; American Airlines manages 65.8%. Sample sizes sit next to every figure, because a two-point gap across 1,471 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 3,701 | 77.6% | 71 min | 0.92% | B+ |
| Envoy Airthin sample | 125 | 76.0% | 52 min | 0.00% | B+ |
| Frontier Airlinesthin sample | 331 | 73.5% | 141 min | 1.81% | C |
| Southwest Airlines | 570 | 72.7% | 70 min | 1.40% | C |
| American Airlines | 1,471 | 65.8% | 78 min | 1.63% | C |
United leads American by 12 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
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 32 points, against 12 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,108 flights89.0%
- 8am–11am1,066 flights79.3%
- 11am–2pm872 flights82.2%
- 2pm–5pm1,426 flights69.5%
- 5pm–8pm726 flights57.2%
- 8pm–5am1,000 flights63.6%
Scale runs 50% to 95%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 57.2% on time, against 89.0% 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.
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.
December is the weak month at 65.5% on time, against 80.4% in September. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days.
Across the week, Tuesday is the strongest day at 77.4% on time and Sunday the weakest at 71.4%. 6 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 44% of the 121,000 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.
- 44%Late-arriving aircraft
- 29%Carrier
- 23%National Airspace System
- 4%Extreme weather
- 0%Security
44% 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 121,000 reported delay minutes here, that single category outweighs weather by 10 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 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 89.0% on time here.
Cancellations sit at 1.16% against a national 1.80%, which is ordinary. Diversions add another 0.27%.
Connections and stage length
What a delay here actually costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 10.1% of arrivals land a full hour or more behind schedule, against 8.2% 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 70.4% on time across 6,192 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.
The sample behind these figures is 6,198 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.
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 December 65.5%, a swing of 15 points. If the dates move at all, move them out of December before you think about anything else.
Common questions
ORD to DEN questions
How often is ORD to DEN delayed?
About one flight in four arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 25.9% of the 6,198 flights in this analysis, against 22.6% 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 77.6% on time across 3,701 flights. American Airlines is at the other end on 65.8%, a gap of 12 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 89.0% on time. The 5pm–8pm window is the weakest at 57.2%, 32 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 December delays on ORD to DEN?
December is the weakest month at 65.5% 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-time record77.6%
- Envoy Air on-time record76.0%
- Frontier Airlines on-time record73.5%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
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.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, June 2025 to May 2026. Updated monthly. How this data is collected.