Route reliability record
ORD→IAD
Chicago to Washington
- Flights
- 2,051
- Period
- July 2025 to June 2026
- Distance
- 588 mi
- Carriers
- 1
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, 4 points worse than the national rate of 77.6%. The late ones land a little over an hour behind schedule. That rests on 2,051 ORD to IAD flights, with a median arrival 2 minutes early.
Best time to fly ORD to IAD: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 98.1% of the time and Tuesday flights 78.2%, against 74.1% for the route overall.
The US average over the same twelve months is 77.6%, 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
74.1%
Arrivals under 15 minutes late, of 2,035 completed flights
Avg delay
73 min
Across delayed arrivals only, not all flights
Cancelled
0.68%
National rate is 1.81%
Best carrier
United
74.1% on time across 2,051 flights
These figures cover 2,051 flights between July 2025 and June 2026. Beyond the headline rate, 9.7% 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 IAD
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 2,051 | 74.1% | 73 min | 0.68% | C+ |
Best ways to make this trip
The most reliable ways to fly Chicago to Washington
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. 4 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. MDW → BWIChicago to Baltimore | Southwest Airlines | 76.7% | 78.9% | 2.83% | 5am–8am, Sat (route) | — |
| 2. ORD → IADChicago to Washington | United Airlines | 73.6% | 74.1% | 0.68% | 5am–8am, Tue | — |
| 3. ORD → BWIChicago to Baltimore | Envoy Air | 73.5% | 76.4% | 3.77% | 5am–8am, Sat | — |
| 4. ORD → BWIChicago to Baltimore | United Airlines | 70.1% | 71.1% | 1.39% | 5am–8am, Thu | — |
| 5. ORD → DCAChicago to Washington | United Airlines | 69.3% | 70.6% | 1.80% | 5am–8am, Sat | UA 1077 06:00 |
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 39 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am54 flights98.1%
- 8am–11am470 flights85.7%
- 11am–2pm459 flights78.9%
- 2pm–5pm419 flights68.8%
- 5pm–8pm365 flights58.8%
- 8pm–5am284 flights70.0%
Scale runs 50% to 100%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 58.8% on time, against 98.1% 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 8am–11am window is the busiest, with 470 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 25 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.
July is the worst month at 58.0% on time, 25 points below June, the best at 83.3%. 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. May was the busiest month here, with 216 flights.
Across the week, Tuesday is the strongest day at 78.2% on time and Sunday the weakest at 69.0%. 9 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
Carriers report a reason for every delay minute they cause, in five DOT categories. The split below is by minutes, not by number of flights, so a handful of very long weather delays weighs as much as many short ones. It covers 38,000 reported delay minutes.
- 36%Late-arriving aircraft
- 34%Carrier
- 24%National Airspace System
- 7%Extreme weather
36% 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 38,000 reported delay minutes here, that single category outweighs weather by 6 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 38,327 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 98.1% on time here.
Cancellations are rare at 0.68%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.
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. 9.7% 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 588 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 runs 75.2% on time across 2,054 flights, within about a point 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 2,051 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 IAD 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. June runs 83.3% on time and July 58.0%, a swing of 25 points. If the dates move at all, move them out of July before you think about anything else. 2,035 completed flights over 12 months sit behind that.
Common questions
ORD to IAD questions
How often is ORD to IAD 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 25.9% of the 2,051 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.
How reliable is ORD to IAD compared with the rest of the country?
74.1% of flights arrive on time here against a national 77.6%, a difference of 4 points against it. That is worth a C+ on this site's grading scale.
What time of day has the fewest delays on ORD to IAD?
The 5am–8am departure window is the strongest at 98.1% on time. The 5pm–8pm window is the weakest at 58.8%, 39 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 July delays on ORD to IAD?
July is the weakest month at 58.0% on time, compared with 83.3% in June. Across the year that is 25 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
- IAD to ORD — the return legseparate record
- Chicago O'Hare International (ORD) delay statistics
- Washington Dulles International (IAD) delay statistics
- ORD to LGA, a related route67.3%
- ATL to IAD, a related route76.5%
- ORD to BOS, a related route67.6%
- United Airlines on-time record74.1%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. ORD to IAD and IAD 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.