Carrier route record
WNBWI→SFO
Southwest Airlines · Baltimore to San Francisco
- Flights
- 365
- Period
- July 2025 to June 2026
- Share of route
- 34%
- Carriers
- 2
Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on BWI to SFO earns a D+, which is as low as this site's scale goes for a reason. Only 57.2% of flights arrive inside the 15-minute window, 20 points worse than the national rate of 77.6%. Late arrivals average about an hour. Treat any tight connection here as a coin flip. That rests on 365 flights, with a median arrival 8 minutes late.
The national on-time rate over the same period is 77.6%, so Southwest on BWI to SFO runs 20 points behind the country as a whole. Across a thousand flights that is about 204 extra late arrivals.
Key figures
On time
57.2%
Arrivals under 15 minutes late, of 360 completed flights
Avg delay
57 min
Across delayed arrivals only, not all flights
Cancelled
0.82%
National rate is 1.81%
Whole route
71.2%
Every carrier on BWI to SFO, 1,086 flights
These figures cover 365 flights between July 2025 and June 2026. Beyond the headline rate, 12.8% 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
Southwest against every carrier on BWI to SFO
Southwest flew 365 of the 1,086 flights on BWI to SFO, about 34% of it. Its 57.2% on time is 14 points worse than the route as a whole, which runs 71.2%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from United at 78.3% to Southwest at 57.2%.
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 |
|---|---|---|---|---|---|
| United Airlines | 721 | 78.3% | 56 min | 0.83% | B+ |
| Southwest Airlines (this page) | 365 | 57.2% | 57 min | 0.82% | D+ |
Departure window
When Southwest runs best on this route
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 39 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–8am—
- 8am–11am82 flights79.0%
- 11am–2pm70 flights62.9%
- 2pm–5pm63 flights58.7%
- 5pm–8pm85 flights43.4%
- 8pm–5am65 flights39.7%
Scale runs 30% to 85%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 39.7% on time, against 79.0% 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 5pm–8pm window is the busiest, with 85 flights scheduled in it.
Across the year
Southwest on BWI to SFO through the year
June is the worst month at 10.0% on time, 77 points below January, the best at 86.7%. 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. January was the busiest month here, with 31 flights.
Across the week, Saturday is the strongest day at 71.2% on time and Sunday the weakest at 50.0%. 21 points is a smaller lever than departure hour, but it is free.
Delay causes
Why Southwest runs late on this route
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 8,831 reported delay minutes.
- 34%Carrier
- 33%Late-arriving aircraft
- 27%National Airspace System
- 5%Extreme weather
The largest share of delay minutes, 34%, 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 3,029 of the 8,831 delay minutes reported here. The split is drawn from 8,831 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 79.0% on time here.
Cancellations are rare at 0.82%, below the national 1.81% and low enough to earn the plus on the grade. Roughly one flight in 100 is called off; the risk here is arriving late, not not arriving.
Connections and stage length
What a delay here costs
For anyone connecting, the number to weigh is not the on-time rate but the tail behind it. 12.8% of arrivals land a full hour or more behind schedule, against 8.1% nationally. A 45-minute layover does not survive that, and no amount of walking quickly changes it. Ninety minutes is the honest minimum here, and two hours if the onward flight is on a separate ticket.
At 2,457 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 65.7% on time across 365 flights, 9 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 9 points of difference.
One caution: this is a thin sample. 365 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.
What to do with this
Booking Southwest on BWI to SFO
Put together: treat all of this as provisional. 365 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 57.2% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 360 completed flights over 12 months sit behind that.
Related
Where to go next
- BWI to SFO, every carrier
- Southwest on SFO to BWI, the return leg
- United Airlines on BWI to SFO78.3%
- Southwest Airlines network-wide record
- Baltimore/Washington International Thurgood Marshall (BWI) delay statistics
- San Francisco International (SFO) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
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.