Route reliability record
ORD→SEA
Chicago to Seattle
- Flights
- 5,572
- Period
- July 2025 to June 2026
- Distance
- 1,721 mi
- Carriers
- 4
This route sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 9 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 5,572 flights, of which United Airlines flew 1,535 at 73.6% on time.
United Airlines is the most reliable of the four carriers covered here at 73.6% on time across 1,535 flights.
Key figures
On time
68.5%
Arrivals under 15 minutes late, of 5,478 completed flights
Avg delay
64 min
Across delayed arrivals only, not all flights
Cancelled
1.45%
National rate is 1.81%
Best carrier
United
73.6% on time across 1,535 flights
These figures cover 5,572 flights between July 2025 and June 2026. Beyond the headline rate, 9.5% 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 SEA
The choice of carrier is not cosmetic here. United Airlines arrives on time 73.6% of the time; American Airlines manages 63.5%. Sample sizes sit next to every figure, because a two-point gap across 1,336 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 1,535 | 73.6% | 59 min | 0.72% | C+ |
| Delta Air Lines | 902 | 68.8% | 66 min | 1.44% | C |
| Alaska Airlines | 1,799 | 67.5% | 63 min | 1.67% | C |
| American Airlines | 1,336 | 63.5% | 70 min | 2.02% | D |
United leads American by 10 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 28 points, against 10 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,106 flights80.6%
- 8am–11am1,112 flights71.6%
- 11am–2pm781 flights77.3%
- 2pm–5pm904 flights67.6%
- 5pm–8pm912 flights56.0%
- 8pm–5am757 flights52.3%
Scale runs 45% to 85%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 52.3% on time, against 80.6% 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 1,112 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 36 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 47.9% on time, against 84.2% 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. July was the busiest month here, with 622 flights.
Across the week, Tuesday is the strongest day at 72.3% on time and Sunday the weakest at 65.4%. 7 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 111,000 reported delay minutes.
- 41%Late-arriving aircraft
- 28%Carrier
- 24%National Airspace System
- 7%Extreme weather
- 0%Security
41% 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 111,000 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 111,212 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 80.6% on time here.
Cancellations sit at 1.45% against a national 1.81%, which is ordinary. Diversions add another 0.23%.
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. 9.5% 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.
At 1,721 miles this is transcontinental flying, and long routes get a quiet structural advantage. Scheduled block time on a flight this length carries more padding in absolute minutes, so a twenty-minute late departure often still becomes an on-time arrival. Read the on-time rate here as slightly flattering next to a short-haul route with the same operational quality.
The return leg is a different operation and performs like one: it runs 75.0% on time across 5,566 flights, 7 points above 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 7 points of difference.
The sample behind these figures is 5,572 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 84.2% on time and December 47.9%, a swing of 36 points. If the dates move at all, move them out of December before you think about anything else. 5,478 completed flights over 12 months sit behind that.
Common questions
ORD to SEA questions
How often is ORD to SEA delayed?
About one flight in three arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 31.5% of the 5,572 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on ORD to SEA?
United Airlines leads at 73.6% on time across 1,535 flights. American Airlines is at the other end on 63.5%, a gap of 10 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 SEA?
The 5am–8am departure window is the strongest at 80.6% on time. The 8pm–5am window is the weakest at 52.3%, 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 December delays on ORD to SEA?
December is the weakest month at 47.9% on time, compared with 84.2% in September. Across the year that is 36 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
- SEA to ORD — the return legseparate record
- Chicago O'Hare International (ORD) delay statistics
- Seattle-Tacoma International (SEA) delay statistics
- United Airlines on-time record73.6%
- Delta Air Lines on-time record68.8%
- Alaska Airlines on-time record67.5%
- 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 SEA and SEA 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, July 2025 to June 2026. Updated monthly. How this data is collected.