Route reliability record
MDW→SAN
Chicago to San Diego
- Flights
- 1,079
- Period
- July 2025 to June 2026
- Distance
- 1,728 mi
- Carriers
- 1
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, 5 points worse than the national rate of 77.6%. The late ones land about 45 minutes behind schedule. That rests on 1,079 MDW to SAN flights, with a median arrival 2 minutes late.
Best time to fly MDW to SAN: a 5am–8am departure, ideally on a Wednesday. Flights in that window arrived on time 90.2% of the time and Wednesday flights 80.6%, against 72.5% for the route overall.
The national on-time rate over the same period is 77.6%, so this route runs 5 points behind the country as a whole. Across a thousand flights that is about 51 extra late arrivals.
Key figures
On time
72.5%
Arrivals under 15 minutes late, of 1,061 completed flights
Avg delay
46 min
Across delayed arrivals only, not all flights
Cancelled
1.30%
National rate is 1.81%
Best carrier
Southwest
72.5% on time across 1,079 flights
These figures cover 1,079 flights between July 2025 and June 2026. On-time means an arrival less than 15 minutes after the scheduled gate time, the same threshold the Department of Transportation uses in its own reports. Cancelled and diverted flights are excluded from the on-time rate and counted separately, which is why the cancellation column matters on its own.
Carrier by carrier
Which airline is most reliable on MDW to SAN
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 | 1,079 | 72.5% | 46 min | 1.30% | C |
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. 3 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 | 76.8% | 77.0% | 0.30% | 5am–8am, Tue | UA 660 08:46 |
| 2. MDW → SANChicago to San Diego | Southwest Airlines | 71.6% | 72.5% | 1.30% | 5am–8am, Wed | — |
| 3. ORD → SANChicago to San Diego | Alaska Airlines | 66.8% | 68.4% | 2.33% | 8am–11am, Sat | — |
| 4. ORD → SANChicago to San Diego | American Airlines | 65.2% | 66.3% | 1.73% | 5am–8am, Tue | AA 2131 10:05 |
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 25 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–8am196 flights90.2%
- 8am–11am274 flights70.6%
- 11am–2pm106 flights75.2%
- 2pm–5pm163 flights65.8%
- 5pm–8pm115 flights66.4%
- 8pm–5am225 flights65.7%
Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.
Book the early departure. Flights leaving between 5am–8am arrive on time 90.2% of the time, against 65.7% for the overnight window. That is 25 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8am–11am window is the busiest, with 274 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 35 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.
June is the worst month at 50.0% on time, 35 points below October, the best at 85.1%. 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, Wednesday is the strongest day at 80.6% on time and Sunday the weakest at 69.6%. 11 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 13,000 reported delay minutes.
- 36%Late-arriving aircraft
- 36%Carrier
- 25%National Airspace System
- 1%Security
- 1%Extreme weather
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 13,000 reported delay minutes here, that single category outweighs weather by 36 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 13,411 reported delay minutes.
The largest share of delay minutes, 36%, 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 4,872 of the 13,000 delay minutes reported here.
Cancellations sit at 1.30% against a national 1.81%, which is ordinary. Diversions add another 0.37%.
Connections and stage length
What a delay here actually costs
5.6% 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 45 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 78.1% on time across 1,080 flights, 6 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 6 points of difference.
One caution: this is a thin sample. 1,079 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 SAN after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 1,079 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 72.5% 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
MDW to SAN questions
How often is MDW to SAN delayed?
Roughly one flight in four arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 27.5% of the 1,079 flights in this analysis, against 22.4% nationally. Delayed flights are late by about 45 minutes on average.
How reliable is MDW to SAN compared with the rest of the country?
72.5% of flights arrive on time here against a national 77.6%, a difference of 5 points against it. That is worth a C on this site's grading scale.
What time of day has the fewest delays on MDW to SAN?
The 5am–8am departure window is the strongest at 90.2% on time. The 8pm–5am window is the weakest at 65.7%, 25 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 June delays on MDW to SAN?
June is the weakest month at 50.0% on time, compared with 85.1% in October. Across the year that is 35 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 MDW — the return legseparate record
- Chicago Midway International (MDW) delay statistics
- San Diego International (SAN) delay statistics
- MDW to ATL, a related route79.8%
- SFO to SAN, a related route66.6%
- MDW to PHX, a related route75.0%
- Southwest Airlines on-time record72.5%
- 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. MDW to SAN and SAN to MDW 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, July 2025 to June 2026. Last updated 15 September 2026; recomputed monthly. How this data is collected.