Route reliability record
BWI→SAT
Baltimore to San Antonio
- Flights
- 736
- Period
- July 2025 to June 2026
- Distance
- 1,407 mi
- Carriers
- 2
This route lands a B, about a point worse than the national rate of 77.6%. About 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 736 BWI to SAT flights, with a median arrival 5 minutes early.
Best time to fly BWI to SAT: a 8am–11am departure, ideally on a Tuesday. Flights in that window arrived on time 89.6% of the time and Tuesday flights 83.5%, against 76.8% 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
76.8%
Arrivals under 15 minutes late, of 725 completed flights
Avg delay
57 min
Across delayed arrivals only, not all flights
Cancelled
1.36%
National rate is 1.81%
Best carrier
Southwest
76.8% on time across 735 flights
These figures cover 736 flights between July 2025 and June 2026. The median arrival is 5 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 BWI to SAT
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 |
|---|---|---|---|---|---|
| Spirit Airlinesthin sample | 1 | 100.0% | — | 0.00% | A+ |
| Southwest Airlines | 735 | 76.8% | 57 min | 1.36% | B |
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–8am6 flights—
- 8am–11am264 flights89.6%
- 11am–2pm67 flights82.1%
- 2pm–5pm84 flights69.0%
- 5pm–8pm178 flights68.4%
- 8pm–5am137 flights64.9%
Scale runs 55% to 95%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 64.9% on time, against 89.6% for the 8am–11am 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 264 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 55.4% on time, 35 points below February, the best at 90.6%. 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. July was the busiest month here, with 85 flights.
Across the week, Tuesday is the strongest day at 83.5% on time and Saturday the weakest at 68.6%. 15 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 46% of the 9,612 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.
- 46%Late-arriving aircraft
- 33%Carrier
- 17%National Airspace System
- 4%Extreme weather
- 1%Security
46% 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 9,612 reported delay minutes here, that single category outweighs weather by 11 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 9,612 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 89.6% on time here.
Cancellations sit at 1.36% against a national 1.81%, which is ordinary. Diversions add another 0.14%.
Connections and stage length
What a delay here actually costs
7.6% 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 an hour, which a normal layover absorbs.
The 1,407 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty. It is also long enough that the aircraft usually flies three or four legs a day rather than six, which slows how fast delay compounds.
The return leg is a different operation and performs like one: it runs 80.9% on time across 736 flights, 4 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 4 points of difference.
One caution: this is a thin sample. 736 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 SAT after this flight
What to do with this
Booking this route
Put together: treat all of this as provisional. 736 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 76.8% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 725 completed flights over 12 months sit behind that.
Common questions
BWI to SAT questions
How often is BWI to SAT delayed?
About 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 23.2% of the 736 flights in this analysis, against 22.4% nationally. Delayed flights are late by about an hour on average.
How reliable is BWI to SAT compared with the rest of the country?
76.8% of flights arrive on time here against a national 77.6%, a difference of about a point against it. That is worth a B on this site's grading scale.
What time of day has the fewest delays on BWI to SAT?
The 8am–11am departure window is the strongest at 89.6% on time. The 8pm–5am window is the weakest at 64.9%, 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 BWI to SAT?
June is the weakest month at 55.4% on time, compared with 90.6% in February. 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
- SAT to BWI — the return legseparate record
- Baltimore/Washington International Thurgood Marshall (BWI) delay statistics
- San Antonio International (SAT) delay statistics
- BWI to ATL, a related route80.6%
- DFW to SAT, a related route67.0%
- BWI to MCO, a related route75.6%
- Spirit Airlines on-time record100.0%
- Southwest Airlines on-time record76.8%
- 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. BWI to SAT and SAT to BWI 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.