Route reliability record
SAN→MDW
San Diego to Chicago
- Flights
- 1,080
- Period
- July 2025 to June 2026
- Distance
- 1,728 mi
- Carriers
- 1
This route lands a B+, level with the national rate of 77.6%. Roughly one flight in five arrives 15 minutes late or worse, and those flights are late by roughly 50 minutes on average. That is a workable record, not a spotless one. That rests on 1,080 SAN to MDW flights, with a median arrival 2 minutes early.
Best time to fly SAN to MDW: a 8pm–5am departure, ideally on a Saturday. Flights in that window arrived on time 97.4% of the time and Saturday flights 88.5%, against 78.1% for the route overall.
The US average over the same twelve months is 77.6%, 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
78.1%
Arrivals under 15 minutes late, of 1,061 completed flights
Avg delay
52 min
Across delayed arrivals only, not all flights
Cancelled
0.93%
National rate is 1.81%
Best carrier
Southwest
78.1% on time across 1,080 flights
These figures cover 1,080 flights between July 2025 and June 2026. The median arrival is 2 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
Which airline is most reliable on SAN to MDW
Only one carrier clears this site's 365-flight floor here, so there is no comparison to draw. The table below is the full picture.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Southwest Airlines | 1,080 | 78.1% | 52 min | 0.93% | B+ |
Best ways to make this trip
The most reliable ways to fly San Diego to Chicago
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. 3 of the top 4 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. SAN → ORDSan Diego to Chicago | United Airlines | 81.6% | 82.0% | 0.54% | 8pm–5am, Tue | UA 2343 07:00 |
| 2. SAN → MDWSan Diego to Chicago | Southwest Airlines | 77.4% | 78.1% | 0.93% | 8pm–5am, Sat | — |
| 3. SAN → ORDSan Diego to Chicago | American Airlines | 75.9% | 77.3% | 1.80% | 8pm–5am, Tue | AA 2131 13:12 |
| 4. SAN → ORDSan Diego to Chicago | Alaska Airlines | 71.8% | 73.5% | 2.33% | 5am–8am, Tue | — |
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 43 points, against half a point between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am318 flights90.4%
- 8am–11am157 flights82.4%
- 11am–2pm221 flights71.0%
- 2pm–5pm90 flights54.5%
- 5pm–8pm176 flights60.6%
- 8pm–5am118 flights97.4%
Scale runs 45% to 100%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is the strongest at 97.4% on time. The full set of windows spans 43 points.
Across the year
When delays peak on this route
This route's year swings by 19 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 68.2% on time, 19 points below October, the best at 87.6%. 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. May was the busiest month here, with 105 flights.
Across the week, Saturday is the strongest day at 88.5% on time and Thursday the weakest at 70.7%. 18 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 48% of the 12,000 delay minutes carriers reported, and the remaining four split what is left. The split is by minutes rather than by flights, so a few very long delays count for as much as many short ones.
- 48%Late-arriving aircraft
- 35%Carrier
- 16%National Airspace System
- 1%Security
- 0%Extreme weather
48% 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 12,000 reported delay minutes here, that single category outweighs weather by 48 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 12,054 reported delay minutes.
The largest share of delay minutes, 35%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. Unlike weather, that is a management outcome, and it is the category where the gap between two carriers on the same schedule is genuinely earned. It accounts for 4,244 of the 12,000 delay minutes reported here.
Cancellations sit at 0.93% against a national 1.81%, which is ordinary. Diversions add another 0.83%.
Connections and stage length
What a delay here actually costs
5.7% 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 roughly 50 minutes, which a normal layover absorbs.
At 1,728 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 72.5% on time across 1,079 flights, 6 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 6 points of difference.
One caution: this is a thin sample. 1,080 flights over twelve months is enough to clear this site's floor but not enough to pin the rate down tightly, and a single bad week moves it by more than a point. Treat the grade as a rough reading.
Work out the risk of missing a connection in MDW after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 1,080 flights over twelve months is enough to clear this site's floor and not enough to be confident to better than a couple of points. The 78.1% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 1,061 completed flights over 12 months sit behind that.
Common questions
SAN to MDW questions
How often is SAN to MDW delayed?
Roughly one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 21.9% of the 1,080 flights in this analysis, against 22.4% nationally. Delayed flights are late by roughly 50 minutes on average.
How reliable is SAN to MDW compared with the rest of the country?
78.1% of flights arrive on time here against a national 77.6%, a difference of half a point in its favour. That is worth a B+ on this site's grading scale.
What time of day has the fewest delays on SAN to MDW?
The 8pm–5am departure window is the strongest at 97.4% on time. The 2pm–5pm window is the weakest at 54.5%, 43 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 SAN to MDW?
August is the weakest month at 68.2% on time, compared with 87.6% in October. Across the year that is 19 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
- MDW to SAN — the return legseparate record
- San Diego International (SAN) delay statistics
- Chicago Midway International (MDW) delay statistics
- SAN to SFO, a related route65.0%
- ATL to MDW, a related route76.3%
- SAN to DEN, a related route79.2%
- Southwest Airlines on-time record78.1%
- 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. SAN to MDW and MDW to SAN are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Embed SAN to MDW’s on-time badge on your site
Paste this into a web page. The badge shows the current on-time rate, cancellation rate and grade, and updates every month. Preview it, or build a badge for another route or airport.
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.