Route reliability record
SFO→ORD
San Francisco to Chicago
- Flights
- 5,609
- Period
- June 2025 to May 2026
- Distance
- 1,846 mi
- Carriers
- 3
This route lands a B, level with the national rate of 77.4%. About one flight in four 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 5,609 flights, of which United Airlines flew 3,774 at 78.8% on time.
The US average over the same twelve months is 77.4%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
76.8%
Arrivals under 15 minutes late, of 5,503 completed flights
Avg delay
80 min
Across delayed arrivals only, not all flights
Cancelled
1.32%
National rate is 1.80%
Best carrier
United
78.8% on time across 3,774 flights
These figures cover 5,609 flights between June 2025 and May 2026. Beyond the headline rate, 8.4% 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 SFO to ORD
The two carriers here are closely matched: 5 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 | 3,774 | 78.8% | 68 min | 1.01% | B |
| American Airlines | 1,755 | 73.4% | 101 min | 1.88% | C |
| Alaska Airlinesthin sample | 80 | 61.3% | 52 min | 3.75% | D− |
No carrier stands out. United tops the table at 78.8%, 5 points clear of the bottom, which is inside the range this kind of sample moves year to year.
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 34 points, against 5 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am1,081 flights92.3%
- 8am–11am1,153 flights78.8%
- 11am–2pm717 flights58.5%
- 2pm–5pm953 flights67.2%
- 5pm–8pm518 flights79.2%
- 8pm–5am1,187 flights78.5%
Scale runs 50% to 100%. 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 58.5% on time against 92.3% 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.
Across the year
When delays peak on this route
This route's year swings by 14 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.
July is the worst month at 71.2% on time, 14 points below February, the best at 85.2%. 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.
Across the week, Tuesday is the strongest day at 82.4% on time and Monday the weakest at 72.8%. 10 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 101,000 reported delay minutes.
- 41%Late-arriving aircraft
- 31%Carrier
- 26%National Airspace System
- 1%Extreme weather
- 0%Security
41% 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 101,000 reported delay minutes here, that single category outweighs weather by 32 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 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 92.3% on time here.
Cancellations sit at 1.32% against a national 1.80%, which is ordinary. Diversions add another 0.57%.
Connections and stage length
What a delay here actually costs
8.4% of arrivals land an hour or more late, close to the national 8.2%. 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 1,846 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 70.2% on time across 5,607 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 5,609 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 85.2% on time and July 71.2%, a swing of 14 points. If the dates move at all, move them out of July before you think about anything else.
Common questions
SFO to ORD questions
How often is SFO to ORD delayed?
About one flight in four arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 23.2% of the 5,609 flights in this analysis, against 22.6% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on SFO to ORD?
United Airlines leads at 78.8% on time across 3,774 flights. American Airlines is at the other end on 73.4%, a gap of 5 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 SFO to ORD?
The 5am–8am departure window is the strongest at 92.3% on time. The 11am–2pm window is the weakest at 58.5%, 34 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 SFO to ORD?
July is the weakest month at 71.2% on time, compared with 85.2% in February. Across the year that is 14 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
- ORD to SFO — the return legseparate record
- San Francisco International (SFO) delay statistics
- Chicago O'Hare International (ORD) delay statistics
- United Airlines on-time record78.8%
- American Airlines on-time record73.4%
- Alaska Airlines on-time record61.3%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
Direction matters. SFO to ORD and ORD to SFO 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, June 2025 to May 2026. Updated monthly. How this data is collected.