Route reliability record
ORD→SAN
Chicago to San Diego
- Flights
- 3,807
- Period
- July 2025 to June 2026
- Distance
- 1,723 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, 6 points worse than the national rate of 77.6%. The late ones land about an hour behind schedule. That rests on 3,807 flights, of which United Airlines flew 1,672 at 77.0% on time.
United Airlines is the most reliable of the three carriers covered here at 77.0% on time across 1,672 flights.
Key figures
On time
71.2%
Arrivals under 15 minutes late, of 3,749 completed flights
Avg delay
67 min
Across delayed arrivals only, not all flights
Cancelled
1.18%
National rate is 1.81%
Best carrier
United
77.0% on time across 1,672 flights
These figures cover 3,807 flights between July 2025 and June 2026. Beyond the headline rate, 10.2% 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 ORD to SAN
The choice of carrier is not cosmetic here. United Airlines arrives on time 77.0% of the time; American Airlines manages 66.3%. Sample sizes sit next to every figure, because a two-point gap across 1,385 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines | 1,672 | 77.0% | 64 min | 0.30% | B+ |
| Alaska Airlines | 688 | 68.4% | 70 min | 2.33% | C |
| American Airlines | 1,385 | 66.3% | 65 min | 1.73% | C |
| Frontier Airlinesthin sample | 62 | 53.2% | 103 min | 0.00% | F+ |
United leads American by 11 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 29 points, against 11 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am531 flights86.0%
- 8am–11am980 flights76.2%
- 11am–2pm612 flights72.5%
- 2pm–5pm641 flights67.5%
- 5pm–8pm461 flights64.6%
- 8pm–5am582 flights56.7%
Scale runs 50% to 90%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 56.7% on time, against 86.0% 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 980 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 15 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.
September is the best month on the calendar at 77.8% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. June was the busiest month here, with 380 flights.
Across the week, Tuesday is the strongest day at 76.9% on time and Friday the weakest at 66.1%. 11 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 72,000 reported delay minutes.
- 40%Late-arriving aircraft
- 31%Carrier
- 22%National Airspace System
- 7%Extreme weather
40% 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 72,000 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 72,037 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 86.0% on time here.
Cancellations sit at 1.18% against a national 1.81%, which is ordinary. Diversions add another 0.34%.
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. 10.2% 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 1,723 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 78.0% on time across 3,807 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 3,807 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 77.8% on time and April 62.8%, a swing of 15 points. If the dates move at all, move them out of April before you think about anything else. 3,749 completed flights over 12 months sit behind that.
Common questions
ORD to SAN questions
How often is ORD to SAN delayed?
Roughly 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 28.8% of the 3,807 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 SAN?
United Airlines leads at 77.0% on time across 1,672 flights. American Airlines is at the other end on 66.3%, a gap of 11 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 SAN?
The 5am–8am departure window is the strongest at 86.0% on time. The 8pm–5am window is the weakest at 56.7%, 29 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 April delays on ORD to SAN?
April is the weakest month at 62.8% on time, compared with 77.8% in September. Across the year that is 15 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
- SAN to ORD — the return legseparate record
- Chicago O'Hare International (ORD) delay statistics
- San Diego International (SAN) delay statistics
- United Airlines on-time record77.0%
- Alaska Airlines on-time record68.4%
- American Airlines on-time record66.3%
- 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 SAN and SAN 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.