Route reliability record
IAD→ORD
Washington to Chicago
- Flights
- 2,106
- Period
- September 2025 to August 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, 3 points worse than the national rate of 77.3%. The late ones land a little over an hour behind schedule. That rests on 2,106 IAD to ORD flights, with a median arrival 3 minutes early.
Best time to fly IAD to ORD: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 90.7% of the time and Tuesday flights 78.1%, against 74.7% 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
74.7%
Arrivals under 15 minutes late, of 2,081 completed flights
Avg delay
79 min
Across delayed arrivals only, not all flights
Cancelled
0.90%
National rate is 1.89%
Best carrier
United
74.7% on time across 2,106 flights
These figures cover 2,106 flights between September 2025 and August 2026. Beyond the headline rate, 8.8% 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 IAD to ORD
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 | 2,106 | 74.7% | 79 min | 0.90% | C+ |
Flight by flight
Flights on IAD to ORD
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 Washington to Chicago
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. IAD → ORDWashington to Chicago | United Airlines | 74.0% | 74.7% | 0.90% | 5am–8am, Tue | UA 1775 08:20 |
| 2. BWI → ORDBaltimore to Chicago | United Airlines | 73.5% | 74.3% | 1.12% | 5am–8am, Sat | UA 590 17:32 |
| 3. DCA → MDWWashington to Chicago | Southwest Airlines | 73.4% | 75.5% | 2.76% | 5am–8am, Sat | — |
| 4. BWI → MDWBaltimore to Chicago | Southwest Airlines | 73.3% | 75.1% | 2.38% | 5am–8am, Wed (route) | — |
| 5. BWI → ORDBaltimore to Chicago | Envoy Air | 73.1% | 76.0% | 3.80% | 5am–8am, Sat | — |
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 45 points, against half a point between the best and worst carrier.
- 5am–8am291 flights90.7%
- 8am–11am522 flights86.5%
- 11am–2pm365 flights79.8%
- 2pm–5pm148 flights63.9%
- 5pm–8pm416 flights45.6%
- 8pm–5am364 flights77.4%
Scale runs 35% to 95%.
The 5pm–8pm window is where this operation falls apart: 45.6% on time, against 90.7% 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 522 flights scheduled in it.
Explore
Filter IAD to ORD 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 IAD to ORD, the best departure window is 5am–8am at 90.7% on time and the worst is 5pm–8pm at 45.6%, a wide gap of 45.1 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am90.7%
- 8–11am86.5%
- 11am–2pm79.8%
- 2–5pm63.9%
- 5–8pm45.6%
- 8pm–5am77.4%
best all US flightsScale 35% to 95%.
Across the year
When delays peak on this route
This route's year swings by 13 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 66.5% on time, 13 points below June, the best at 79.4%. 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. May was the busiest month here, with 217 flights.
Across the week, Tuesday is the strongest day at 78.1% on time and Sunday the weakest at 70.4%, a spread of 8 points.
Delay causes
Why this route gets delayed
National Airspace System accounts for 59% of the 42,000 delay minutes carriers reported here, and the remaining four split what is left.
- 59%National Airspace System
- 20%Late-arriving aircraft
- 18%Carrier
- 4%Extreme weather
59% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 24,000 minutes out of 42,000, against a national NAS share of 21%. The split is drawn from 41,628 reported delay minutes.
Cancellations sit at 0.90% against a national 1.89%, which is ordinary. Diversions add another 0.28%.
Connections and stage length
What a delay here actually costs
8.8% of arrivals land an hour or more late, close to the national 8.3%, so a 60 to 75 minute layover is reasonable here while anything under 45 minutes is a bet. Most delays on this route last a little over an hour, which a normal layover absorbs.
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.
The return leg runs 75.9% on time across 2,103 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 2,106 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 ORD 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 79.4% on time and July 66.5%, a swing of 13 points. If the dates move at all, move them out of July before you think about anything else. 2,081 completed flights over 12 months sit behind that.
Common questions
IAD to ORD questions
How often is IAD to ORD 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 25.3% of the 2,106 flights in this analysis, against 22.7% nationally. Delayed flights are late by a little over an hour on average.
How reliable is IAD to ORD compared with the rest of the country?
74.7% of flights arrive on time here against a national 77.3%, a difference of 3 points against it. That is worth a C+ on this site's grading scale.
What time of day has the fewest delays on IAD to ORD?
The 5am–8am departure window is the strongest at 90.7% on time. The 5pm–8pm window is the weakest at 45.6%, 45 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 IAD to ORD?
July is the weakest month at 66.5% on time, compared with 79.4% in June. Across the year that is 13 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
- ORD to IAD — the return legseparate record
- Washington Dulles International (IAD) delay statistics
- Chicago O'Hare International (ORD) delay statistics
- IAD to ATL, a related route78.0%
- LGA to ORD, a related route66.7%
- IAD to DEN, a related route83.1%
- United Airlines on-time record74.7%
- The best time of day to fly, according to 7.05 million flight records
- Connecting flights: how much buffer the data says you need
Direction matters. IAD to ORD and ORD to IAD 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.