Route reliability record
SEA→ORD
Seattle to Chicago
- Flights
- 5,538
- Period
- September 2025 to August 2026
- Distance
- 1,721 mi
- Carriers
- 4
This route lands a B, level with the national rate of 77.3%. About one flight in four arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That rests on 5,538 SEA to ORD flights, of which United Airlines flew 1,488 at 81.6% on time.
Best time to fly SEA to ORD: a 5am–8am departure, ideally on a Tuesday. Flights in that window arrived on time 87.3% of the time and Tuesday flights 84.0%, against 76.7% for the route overall.
United Airlines is the most reliable of the four carriers covered here at 81.6% on time across 1,488 flights.
Key figures
On time
76.7%
Arrivals under 15 minutes late, of 5,417 completed flights
Avg delay
79 min
Across delayed arrivals only, not all flights
Cancelled
1.17%
National rate is 1.89%
Best carrier
United
81.6% on time across 1,488 flights
These figures cover 5,538 flights between September 2025 and August 2026. Beyond the headline rate, 8.4% 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 SEA to ORD
The choice of carrier is not cosmetic here. United Airlines arrives on time 81.6% of the time; Alaska Airlines manages 73.8%. Sample sizes sit next to every figure, because a two-point gap across 1,775 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 1,488 | 81.6% | 88 min | 0.81% | B+ |
| Delta Air Lines | 922 | 75.7% | 73 min | 1.30% | B |
| American Airlines | 1,353 | 75.6% | 102 min | 1.55% | B |
| Alaska Airlines | 1,775 | 73.8% | 59 min | 1.13% | C |
United leads Alaska by 8 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Flight by flight
Flights on SEA 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 Seattle to Chicago
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. SEA → ORDSeattle to Chicago | United Airlines | 80.9% | 81.6% | 0.81% | 5am–8am, Sat | UA 2618 07:00 |
| 2. SEA → ORDSeattle to Chicago | Delta Air Lines | 74.7% | 75.7% | 1.30% | 5am–8am, Wed | DL 2055 07:10 |
| 3. SEA → ORDSeattle to Chicago | American Airlines | 74.4% | 75.6% | 1.55% | 5am–8am, Tue | — |
| 4. SEA → ORDSeattle to Chicago | Alaska Airlines | 73.0% | 73.8% | 1.13% | 8pm–5am, Tue | AS 538 17:48 |
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 21 points, against 8 points between the best and worst carrier.
- 5am–8am1,089 flights87.3%
- 8am–11am1,005 flights71.5%
- 11am–2pm995 flights69.8%
- 2pm–5pm719 flights66.1%
- 5pm–8pm845 flights77.8%
- 8pm–5am885 flights84.7%
Scale runs 60% to 95%.
Book the early departure. Flights leaving between 5am–8am arrive on time 87.3% of the time, against 66.1% for the afternoon window. That is 21 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5am–8am window is the busiest, with 1,089 flights scheduled in it.
Explore
Filter SEA 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 SEA to ORD, the best departure window is 5am–8am at 87.3% on time and the worst is 2pm–5pm at 66.1%, a wide gap of 21.2 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am87.3%
- 8–11am71.5%
- 11am–2pm69.8%
- 2–5pm66.1%
- 5–8pm77.8%
- 8pm–5am84.7%
best all US flightsScale 60% to 95%.
Across the year
When delays peak on this route
This route's year swings by 22 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 70.1% on time, against 92.3% in February. 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, Tuesday is the strongest day at 84.0% on time and Sunday the weakest at 70.0%, a spread of 14 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 99,000 reported delay minutes.
- 36%National Airspace System
- 36%Carrier
- 26%Late-arriving aircraft
- 3%Extreme weather
The largest share of delay minutes, 36%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 35,000 of the 99,000 delay minutes reported here. The split is drawn from 99,296 reported delay minutes.
36% 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 35,000 minutes out of 99,000, against a national NAS share of 21%.
Cancellations sit at 1.17% against a national 1.89%, which is ordinary. Diversions add another 1.01%.
Connections and stage length
What a delay here actually costs
8.4% 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.
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 67.5% on time across 5,542 flights, 9 points below 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 5,538 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. February runs 92.3% on time and December 70.1%, a swing of 22 points. If the dates move at all, move them out of December before you think about anything else. 5,417 completed flights over 12 months sit behind that.
Common questions
SEA to ORD questions
How often is SEA 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 23.3% of the 5,538 flights in this analysis, against 22.7% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on SEA to ORD?
United Airlines leads at 81.6% on time across 1,488 flights. Alaska Airlines is at the other end on 73.8%, a gap of 8 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 SEA to ORD?
The 5am–8am departure window is the strongest at 87.3% on time. The 2pm–5pm window is the weakest at 66.1%, 21 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 SEA to ORD?
December is the weakest month at 70.1% on time, compared with 92.3% in February. Across the year that is 22 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 SEA — the return legseparate record
- Seattle-Tacoma International (SEA) delay statistics
- Chicago O'Hare International (ORD) delay statistics
- United Airlines on SEA to ORD81.6%
- Delta Air Lines on SEA to ORD75.7%
- American Airlines on SEA to ORD75.6%
- Alaska Airlines on SEA to ORD73.8%
- SEA to LAX, a related route82.0%
- LGA to ORD, a related route66.7%
- SEA to PHX, a related route78.2%
- United Airlines on-time record81.6%
- Delta Air Lines on-time record75.7%
- American Airlines on-time record75.6%
- The best time of day to fly, according to 7.05 million flight records
- Worst months to fly in the US, ranked by the data
Direction matters. SEA to ORD and ORD to SEA 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.