Carrier route record
UAORD→SAN
United Airlines · Chicago to San Diego
- Flights
- 1,672
- Period
- July 2025 to June 2026
- Share of route
- 44%
- Carriers
- 4
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with United Airlines.
United on ORD to SAN 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 about an hour on average. That is a workable record, not a spotless one. That rests on 1,672 flights. The strongest carrier on the route with a full sample, Alaska Airlines, flew 688 at 68.4% on time.
The US average over the same twelve months is 77.6%, so there is little to separate United on ORD to SAN from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
77.0%
Arrivals under 15 minutes late, of 1,659 completed flights
Avg delay
64 min
Across delayed arrivals only, not all flights
Cancelled
0.30%
National rate is 1.81%
Whole route
71.2%
Every carrier on ORD to SAN, 3,807 flights
These figures cover 1,672 flights between July 2025 and June 2026. The median arrival is 4 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.
Carrier by carrier
United against every carrier on ORD to SAN
United flew 1,672 of the 3,807 flights on ORD to SAN, about 44% of it. Its 77.0% on time is 6 points better than the route as a whole, which runs 71.2%. Ranked by on-time rate it is first of four carriers on the route, where the range runs from United at 77.0% to Frontier at 53.2%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.
The two carriers here are closely matched: 2 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| United Airlines (this page) | 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+ |
No carrier stands out. Alaska tops the table at 68.4%, 2 points clear of the bottom, which is inside the range this kind of sample moves year to year.
Flight by flight
United flight numbers on ORD to SAN
Departure window
When United runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 29 points, against 2 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am340 flights89.9%
- 8am–11am365 flights83.6%
- 11am–2pm305 flights80.3%
- 2pm–5pm335 flights65.9%
- 5pm–8pm104 flights72.3%
- 8pm–5am223 flights60.5%
Scale runs 50% to 95%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 60.5% on time, against 89.9% 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 365 flights scheduled in it.
Across the year
United on ORD to SAN through the year
December is the weak month at 70.8% on time, against 85.2% in May. 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. October was the busiest month here, with 155 flights.
Across the week, Tuesday is the strongest day at 83.4% on time and Friday the weakest at 71.0%. 12 points is a smaller lever than departure hour, but it is free.
Delay causes
Why United runs late on this route
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 25,000 reported delay minutes.
- 39%Late-arriving aircraft
- 28%Carrier
- 25%National Airspace System
- 8%Extreme weather
39% 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 25,000 reported delay minutes here, that single category outweighs weather by 5 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 24,502 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 89.9% on time here.
Cancellations are rare at 0.30%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.
Connections and stage length
What a delay here costs
7.3% 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 about an hour, which a normal layover absorbs.
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 82.0% on time across 1,672 flights, 5 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 5 points of difference.
The sample behind these figures is 1,672 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 United on ORD to SAN
Put together: the calendar is the biggest lever here, not the carrier or the hour. May runs 85.2% on time and December 70.8%, a swing of 14 points. If the dates move at all, move them out of December before you think about anything else. 1,659 completed flights over 12 months sit behind that.
Related
Where to go next
- ORD to SAN, every carrier
- United on SAN to ORD, the return leg
- Alaska Airlines on ORD to SAN68.4%
- American Airlines on ORD to SAN66.3%
- United Airlines network-wide record
- Chicago O'Hare International (ORD) delay statistics
- San Diego International (SAN) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
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.