Route reliability record
ORD→SAN
Chicago to San Diego
- Flights
- 3,945
- Period
- September 2025 to August 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, 7 points worse than the national rate of 77.3%. The late ones land about an hour behind schedule. That rests on 3,945 ORD to SAN flights, of which United Airlines flew 1,677 at 76.4% on time.
Best time to fly ORD to SAN: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 88.9% of the time and Saturday flights 79.4%, against 70.5% for the route overall.
United Airlines is the most reliable of the three carriers covered here at 76.4% on time across 1,677 flights.
Key figures
On time
70.5%
Arrivals under 15 minutes late, of 3,881 completed flights
Avg delay
66 min
Across delayed arrivals only, not all flights
Cancelled
1.29%
National rate is 1.89%
Best carrier
United
76.4% on time across 1,677 flights
These figures cover 3,945 flights between September 2025 and August 2026. Beyond the headline rate, 10.2% 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 SAN
The choice of carrier is not cosmetic here. United Airlines arrives on time 76.4% of the time; American Airlines manages 64.3%. Sample sizes sit next to every figure, because a two-point gap across 1,400 flights means less than a ten-point one.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Frontier Airlinesthin sample | 6 | 100.0% | — | 0.00% | A+ |
| United Airlines | 1,677 | 76.4% | 62 min | 0.42% | B+ |
| Alaska Airlines | 862 | 68.7% | 73 min | 2.55% | C |
| American Airlines | 1,400 | 64.3% | 64 min | 1.57% | D |
The spread between United and American is 12 points, wide enough that it should decide the booking. On a hundred trips that is 12 more arrivals inside the on-time window.
Flight by flight
Flights on ORD to SAN
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 San Diego
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 1 of the top 4 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. ORD → SANChicago to San Diego | United Airlines | 76.1% | 76.4% | 0.42% | 5am–8am, Sat | UA 660 08:46 |
| 2. MDW → SANChicago to San Diego | Southwest Airlines | 68.4% | 69.2% | 1.17% | 5am–8am, Wed | — |
| 3. ORD → SANChicago to San Diego | Alaska Airlines | 66.9% | 68.7% | 2.55% | 5am–8am, Sat | AS 1470 08:20 |
| 4. ORD → SANChicago to San Diego | American Airlines | 63.3% | 64.3% | 1.57% | 5am–8am, Sat | — |
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 33 points, against 12 points between the best and worst carrier.
- 5am–8am596 flights88.9%
- 8am–11am975 flights74.6%
- 11am–2pm555 flights73.5%
- 2pm–5pm679 flights65.5%
- 5pm–8pm500 flights61.9%
- 8pm–5am640 flights55.7%
Scale runs 45% to 95%.
The 8pm–5am window is where this operation falls apart: 55.7% on time, against 88.9% 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 975 flights scheduled in it.
Explore
Filter ORD to SAN 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 SAN, the best departure window is 5am–8am at 88.9% on time and the worst is 8pm–5am at 55.7%, a wide gap of 33.2 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am88.9%
- 8–11am74.6%
- 11am–2pm73.5%
- 2–5pm65.5%
- 5–8pm61.9%
- 8pm–5am55.7%
best all US flightsScale 45% to 95%.
Across the year
When delays peak on this route
This route's year swings by 18 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.
August is the worst month at 60.3% on time, 18 points below September, the best at 77.8%. Summer afternoon convection and peak-season schedules land on the same weeks every year, so this is a pattern you can book around rather than a run of bad luck. July was the busiest month here, with 398 flights.
Across the week, Saturday is the strongest day at 79.4% on time and Friday the weakest at 63.8%, a spread of 16 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 75,000 reported delay minutes.
- 42%Late-arriving aircraft
- 27%Carrier
- 25%National Airspace System
- 7%Extreme weather
42% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 75,000 reported delay minutes here, that single category outweighs weather by 6 to one. The split is drawn from 75,036 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 88.9% on time here.
Cancellations sit at 1.29% against a national 1.89%, which is ordinary. Diversions add another 0.33%.
Connections and stage length
What a delay here actually costs
10.2% 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 1,723 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 77.6% on time across 3,944 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 3,945 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 SAN 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 77.8% on time and August 60.3%, a swing of 18 points. If the dates move at all, move them out of August before you think about anything else. 3,881 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 arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 29.5% of the 3,945 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 SAN?
United Airlines leads at 76.4% on time across 1,677 flights. American Airlines is at the other end on 64.3%, a gap of 12 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 88.9% on time. The 8pm–5am window is the weakest at 55.7%, 33 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 August delays on ORD to SAN?
August is the weakest month at 60.3% on time, compared with 77.8% in September. Across the year that is 18 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 ORD to SAN76.4%
- Alaska Airlines on ORD to SAN68.7%
- American Airlines on ORD to SAN64.3%
- ORD to LGA, a related route66.6%
- SFO to SAN, a related route62.2%
- ORD to BOS, a related route66.6%
- Frontier Airlines on-time record100.0%
- United Airlines on-time record76.4%
- Alaska Airlines on-time record68.7%
- Why the first flight of the morning is statistically safest
- Same route, different airline: where the carrier you pick matters most
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.
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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.