Route reliability record

SAN→ORD

San Diego to Chicago

Flights: 3,807
Period: July 2025 to June 2026
Distance: 1,723 mi
Carriers: 4

This route lands a B, level with the national rate of 77.6%. Roughly one flight in five arrive 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 3,807 flights, of which United Airlines flew 1,672 at 82.0% on time.

United Airlines is the most reliable of the three carriers covered here at 82.0% on time across 1,672 flights.

On time

78.0%

Arrivals under 15 minutes late, of 3,716 completed flights

Avg delay

81 min

Across delayed arrivals only, not all flights

Cancelled

1.34%

National rate is 1.81%

Best carrier

United

82.0% on time across 1,672 flights

These figures cover 3,807 flights between July 2025 and June 2026. Beyond the headline rate, 8.1% 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 SAN to ORD

The choice of carrier is not cosmetic here. United Airlines arrives on time 82.0% of the time; Alaska Airlines manages 73.5%. Sample sizes sit next to every figure, because a two-point gap across 688 flights means less than a ten-point one.

On-time performance by carrier on SAN to ORD
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	1,672	82.0%	76 min	0.54%	B+
American Airlines	1,386	77.3%	93 min	1.80%	B
Alaska Airlines	688	73.5%	64 min	2.33%	C
Frontier Airlinesthin sample	61	38.3%	111 min	1.64%	F

United leads Alaska by 9 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 9 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am813 flights86.9%
8am–11am506 flights80.0%
11am–2pm736 flights70.6%
2pm–5pm820 flights65.2%
5pm–8pm448 flights77.6%
8pm–5am484 flights94.6%

Scale runs 55% to 100%. Rows with fewer than 30 flights show a dash.

The overnight block holds up unusually well at 94.6% on time across 484 flights. Red-eyes fly into empty airspace and empty gates, and they are the first rotation of the aircraft's day rather than the last. The 2pm–5pm window is the busiest, with 820 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.

Darker means more delays. Figures are on-time percentages.February best, July worst

July is the worst month at 71.3% on time, 15 points below February, the best at 85.9%. 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. June was the busiest month here, with 380 flights.

Across the week, Tuesday is the strongest day at 84.8% on time and Sunday the weakest at 72.6%. 12 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 66,000 reported delay minutes.

Late-arriving aircraft
36%
National Airspace System
33%
Carrier
25%
Extreme weather
6%

36% 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 66,000 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 66,175 reported delay minutes.

33% 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 22,000 minutes out of 66,000, against a national NAS share of 21%.

Cancellations sit at 1.34% against a national 1.81%, which is ordinary. Diversions add another 1.05%.

Connections and stage length

What a delay here actually costs

8.1% 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 are the a little over an hour kind, 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 71.2% on time across 3,807 flights, 7 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 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. February runs 85.9% on time and July 71.3%, a swing of 15 points. If the dates move at all, move them out of July before you think about anything else. 3,716 completed flights over 12 months sit behind that.

Common questions

SAN to ORD questions

How often is SAN to ORD delayed?

Roughly one flight in five arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 22.0% of the 3,807 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.

Which airline is most reliable on SAN to ORD?

United Airlines leads at 82.0% on time across 1,672 flights. Alaska Airlines is at the other end on 73.5%, a gap of 9 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 SAN to ORD?

The 8pm–5am departure window is the strongest at 94.6% on time. The 2pm–5pm window is the weakest at 65.2%, 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 July delays on SAN to ORD?

July is the weakest month at 71.3% on time, compared with 85.9% in February. 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.

Where to go next

Direction matters. SAN to ORD and ORD to SAN 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.

Key figures