Route reliability record
IAD→ORD
Washington to Chicago
- Flights
- 2,054
- Period
- July 2025 to June 2026
- Distance
- 588 mi
- Carriers
- 1
This route sits in the middle of the pack with a B+. Close to three flights in four arrive on time by the DOT's definition, 2 points worse than the national rate of 77.6%. The late ones land a little over an hour behind schedule. That rests on 2,054 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 93.1% of the time and Tuesday flights 78.8%, against 75.2% 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
75.2%
Arrivals under 15 minutes late, of 2,032 completed flights
Avg delay
73 min
Across delayed arrivals only, not all flights
Cancelled
0.83%
National rate is 1.81%
Best carrier
United
75.2% on time across 2,054 flights
These figures cover 2,054 flights between July 2025 and June 2026. Beyond the headline rate, 8.2% 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
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 | 2,054 | 75.2% | 73 min | 0.83% | B+ |
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.
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. DCA → MDWWashington to Chicago | Southwest Airlines | 75.1% | 77.2% | 2.76% | 5am–8am, Sat | — |
| 2. IAD → ORDWashington to Chicago | United Airlines | 74.6% | 75.2% | 0.83% | 5am–8am, Tue | UA 1775 08:20 |
| 3. BWI → MDWBaltimore to Chicago | Southwest Airlines | 74.4% | 76.0% | 2.10% | 5am–8am, Wed (route) | — |
| 4. BWI → ORDBaltimore to Chicago | United Airlines | 74.1% | 75.1% | 1.31% | 5am–8am, Tue | UA 590 17:20 |
| 5. DCA → ORDWashington to Chicago | United Airlines | 72.0% | 73.6% | 2.21% | 8am–11am, Sat | UA 2201 10:30 |
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 46 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–8am290 flights93.1%
- 8am–11am461 flights85.9%
- 11am–2pm365 flights80.3%
- 2pm–5pm143 flights67.6%
- 5pm–8pm429 flights46.6%
- 8pm–5am366 flights79.1%
Scale runs 40% to 100%. Rows with fewer than 30 flights show a dash.
The 5pm–8pm window is where this operation falls apart: 46.6% on time, against 93.1% 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 461 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 16 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 63.7% on time, 16 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 78.8% on time and Sunday the weakest at 72.2%. 7 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. National Airspace System accounts for 57% of the 37,000 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.
- 57%National Airspace System
- 18%Late-arriving aircraft
- 18%Carrier
- 7%Extreme weather
57% 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 21,000 minutes out of 37,000, against a national NAS share of 21%. The split is drawn from 36,839 reported delay minutes.
Cancellations are rare at 0.83%, 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
8.2% of arrivals land an hour or more late, close to the national 8.1%. That is the figure that decides a connection, and it says 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. 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 74.1% on time across 2,051 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 2,054 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 63.7%, a swing of 16 points. If the dates move at all, move them out of July before you think about anything else. 2,032 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 24.8% of the 2,054 flights in this analysis, against 22.4% 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?
75.2% of flights arrive on time here against a national 77.6%, a difference of 2 points against it. That is worth a B+ 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 93.1% on time. The 5pm–8pm window is the weakest at 46.6%, 46 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 63.7% on time, compared with 79.4% in June. Across the year that is 16 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 route79.2%
- LGA to ORD, a related route67.3%
- IAD to DEN, a related route81.7%
- United Airlines on-time record75.2%
- The best time of day to fly, according to 7.04 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.