Carrier route record
DLSEA→ORD
Delta Air Lines · Seattle to Chicago
- Flights
- 902
- Period
- July 2025 to June 2026
- Share of route
- 16%
- Carriers
- 4
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Delta Air Lines.
Delta on SEA to ORD lands a B, level with the national rate of 77.6%. Roughly one flight in four arrives 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 902 flights. The strongest carrier on the route with a full sample, United Airlines, flew 1,534 at 79.8% on time.
United Airlines is the most reliable of the three carriers covered here at 79.8% on time across 1,534 flights.
Key figures
On time
77.5%
Arrivals under 15 minutes late, of 879 completed flights
Avg delay
71 min
Across delayed arrivals only, not all flights
Cancelled
1.22%
National rate is 1.81%
Whole route
75.0%
Every carrier on SEA to ORD, 5,566 flights
These figures cover 902 flights between July 2025 and June 2026. Beyond the headline rate, 8.6% 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
Delta against every carrier on SEA to ORD
Delta flew 902 of the 5,566 flights on SEA to ORD, about 16% of it. Its 77.5% on time is 3 points better than the route as a whole, which runs 75.0%. Ranked by on-time rate it is number two of four carriers on the route, where the range runs from United at 79.8% to American at 71.2%.
The choice of carrier is not cosmetic here. United Airlines arrives on time 79.8% of the time; American Airlines manages 71.2%. 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 | 1,534 | 79.8% | 81 min | 0.91% | B+ |
| Delta Air Lines (this page) | 902 | 77.5% | 71 min | 1.22% | B |
| Alaska Airlines | 1,794 | 72.3% | 55 min | 1.06% | C |
| American Airlines | 1,336 | 71.2% | 93 min | 2.02% | C |
United leads American by 9 points. Real, but small enough that a better departure time on the weaker carrier can outweigh it.
Flight by flight
Delta flight numbers on SEA to ORD
Departure window
When Delta runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 18 points, against 9 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am328 flights84.7%
- 8am–11am77 flights71.6%
- 11am–2pm134 flights67.2%
- 2pm–5pm7 flights—
- 5pm–8pm356 flights76.0%
- 8pm–5am—
Scale runs 60% to 90%. Rows with fewer than 30 flights show a dash.
The weak window here is the middle of the day, not the evening: 11am–2pm runs 67.2% on time against 84.7% for 5am–8am. That shape usually means a departure bank rather than an accumulating delay, so the recovery later in the afternoon is real rather than noise. The 5pm–8pm window is the busiest, with 356 flights scheduled in it.
Across the year
Delta on SEA to ORD through the year
December is the weak month at 54.9% on time, against 91.8% 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. May was the busiest month here, with 92 flights.
Across the week, Wednesday is the strongest day at 84.3% on time and Sunday the weakest at 69.5%. 15 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Delta runs late on this route
One category carries most of the weight here. Carrier accounts for 46% of the 14,000 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.
- 46%Carrier
- 34%National Airspace System
- 20%Late-arriving aircraft
The largest share of delay minutes, 46%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 6,411 of the 14,000 delay minutes reported here. The split is drawn from 14,041 reported delay minutes.
34% 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 4,801 minutes out of 14,000, against a national NAS share of 21%.
Cancellations sit at 1.22% against a national 1.81%, which is ordinary. Diversions add another 1.33%.
Connections and stage length
What a delay here costs
8.6% 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.
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 68.8% on time across 902 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.
One caution: this is a thin sample. 902 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.
What to do with this
Booking Delta on SEA to ORD
Put together: treat all of this as provisional. 902 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 77.5% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 879 completed flights over 12 months sit behind that.
Related
Where to go next
- SEA to ORD, every carrier
- Delta on ORD to SEA, the return leg
- United Airlines on SEA to ORD79.8%
- Alaska Airlines on SEA to ORD72.3%
- American Airlines on SEA to ORD71.2%
- Delta Air Lines network-wide record
- Seattle-Tacoma International (SEA) delay statistics
- Chicago O'Hare International (ORD) delay statistics
- The best time of day to fly, according to 7.04 million flight records
- Connecting flights: how much buffer the data says you need
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.