Route reliability record
ORD→SEA
Chicago to Seattle
- Flights
- 5,542
- Period
- September 2025 to August 2026
- Distance
- 1,721 mi
- Carriers
- 4
This route draws a C. About one flight in three arrives at least 15 minutes late, and the typical late arrival is about an hour behind schedule. Build slack into anything you connect to. That rests on 5,542 ORD to SEA flights, of which United Airlines flew 1,489 at 74.0% on time.
Best time to fly ORD to SEA: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 80.4% of the time and Saturday flights 72.4%, against 67.5% for the route overall.
United Airlines is the most reliable of the four carriers covered here at 74.0% on time across 1,489 flights.
Key figures
On time
67.5%
Arrivals under 15 minutes late, of 5,452 completed flights
Avg delay
66 min
Across delayed arrivals only, not all flights
Cancelled
1.37%
National rate is 1.89%
Best carrier
United
74.0% on time across 1,489 flights
These figures cover 5,542 flights between September 2025 and August 2026. Beyond the headline rate, 10.5% 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 ORD to SEA
The choice of carrier is not cosmetic here. United Airlines arrives on time 74.0% of the time; American Airlines manages 64.1%. Sample sizes sit next to every figure, because a two-point gap across 1,353 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 1,489 | 74.0% | 59 min | 0.60% | C+ |
| Delta Air Lines | 922 | 66.0% | 67 min | 1.41% | C |
| Alaska Airlines | 1,778 | 65.4% | 68 min | 1.80% | C |
| American Airlines | 1,353 | 64.1% | 68 min | 1.63% | D |
United leads American by 10 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Flight by flight
Flights on ORD to SEA
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 Chicago to Seattle
Every airline on this route, ranked by how often a scheduled flight actually operated and arrived on time, with its best departure time and most punctual flight number. No nearby airport pair beat these.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. ORD → SEAChicago to Seattle | United Airlines | 73.6% | 74.0% | 0.60% | 5am–8am, Sat | UA 2211 19:45 |
| 2. ORD → SEAChicago to Seattle | Delta Air Lines | 65.1% | 66.0% | 1.41% | 5am–8am, Sat | DL 2041 06:55 |
| 3. ORD → SEAChicago to Seattle | Alaska Airlines | 64.2% | 65.4% | 1.80% | 5am–8am, Sat | AS 587 08:00 |
| 4. ORD → SEAChicago to Seattle | American Airlines | 63.1% | 64.1% | 1.63% | 5am–8am, Tue | — |
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 27 points, against 10 points between the best and worst carrier.
- 5am–8am1,105 flights80.4%
- 8am–11am1,051 flights70.7%
- 11am–2pm803 flights74.7%
- 2pm–5pm898 flights66.2%
- 5pm–8pm940 flights54.7%
- 8pm–5am745 flights53.3%
Scale runs 45% to 85%.
The 8pm–5am window is where this operation falls apart: 53.3% on time, against 80.4% 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 5am–8am window is the busiest, with 1,105 flights scheduled in it.
Explore
Filter ORD to SEA 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 ORD to SEA, the best departure window is 5am–8am at 80.4% on time and the worst is 8pm–5am at 53.3%, a wide gap of 27.1 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am80.4%
- 8–11am70.7%
- 11am–2pm74.7%
- 2–5pm66.2%
- 5–8pm54.7%
- 8pm–5am53.3%
best all US flightsScale 45% to 95%.
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 608 flights.
Across the week, Saturday is the strongest day at 72.4% on time and Monday the weakest at 64.6%, a spread of 8 points.
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 117,000 reported delay minutes.
- 42%Late-arriving aircraft
- 28%Carrier
- 24%National Airspace System
- 6%Extreme weather
- 0%Security
42% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 117,000 reported delay minutes here, that single category outweighs weather by 7 to one. The split is drawn from 117,050 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 80.4% on time here.
Cancellations sit at 1.37% against a national 1.89%, which is ordinary. Diversions add another 0.25%.
Connections and stage length
What a delay here actually costs
10.5% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection 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 76.7% on time across 5,538 flights, 9 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 9 points of difference.
The sample behind these figures is 5,542 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 SEA 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. 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. 5,452 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 arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 32.5% of the 5,542 flights in this analysis, against 22.7% nationally. Delayed flights are late by about an hour on average.
Which airline is most reliable on ORD to SEA?
United Airlines leads at 74.0% on time across 1,489 flights. American Airlines is at the other end on 64.1%, 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 80.4% on time. The 8pm–5am window is the weakest at 53.3%, 27 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 ORD to SEA74.0%
- Delta Air Lines on ORD to SEA66.0%
- Alaska Airlines on ORD to SEA65.4%
- American Airlines on ORD to SEA64.1%
- ORD to LGA, a related route66.6%
- LAX to SEA, a related route85.0%
- ORD to BOS, a related route66.6%
- United Airlines on-time record74.0%
- Delta Air Lines on-time record66.0%
- Alaska Airlines on-time record65.4%
- Why the first flight of the morning is statistically safest
- How often a connection fails at the major US hubs
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.
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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.