Carrier route record
WNBWI→SFO
Southwest Airlines · Baltimore to San Francisco
- Flights
- 365
- Period
- September 2025 to August 2026
- Share of route
- 35%
- Carriers
- 2
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on BWI to SFO earns an F+, which is as low as this site's scale goes for a reason. Only 51.4% of flights arrive inside the 15-minute window, 26 points worse than the national rate of 77.3%. Late arrivals average about 55 minutes. Treat any tight connection here as a coin flip. That rests on 365 flights, with a median arrival 13 minutes late.
The national on-time rate over the same period is 77.3%, so Southwest on BWI to SFO runs 26 points behind the country as a whole. Across a thousand flights that is about 259 extra late arrivals.
Key figures
On time
51.4%
Arrivals under 15 minutes late, of 360 completed flights
Avg delay
55 min
Across delayed arrivals only, not all flights
Cancelled
0.82%
National rate is 1.89%
Whole route
68.5%
Every carrier on BWI to SFO, 1,033 flights
These figures cover 365 flights between September 2025 and August 2026. Beyond the headline rate, 13.6% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
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Carrier by carrier
Southwest against every carrier on BWI to SFO
Southwest flew 365 of the 1,033 flights on BWI to SFO, about 35% of it. Its 51.4% on time is 17 points worse than the route as a whole, which runs 68.5%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from United at 77.9% to Southwest at 51.4%.
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 | 668 | 77.9% | 50 min | 0.90% | B+ |
| Southwest Airlines (this page) | 365 | 51.4% | 55 min | 0.82% | F+ |
Timetable by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
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 27 points, against half a point between the best and worst carrier.
- 5am–8am—
- 8am–11am102 flights66.3%
- 11am–2pm58 flights53.4%
- 2pm–5pm58 flights50.0%
- 5pm–8pm82 flights41.2%
- 8pm–5am65 flights39.7%
Scale runs 30% to 70%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 39.7% on time, against 66.3% 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 102 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 69.2% on time and Sunday the weakest at 40.0%, a spread of 29 points.
Arrival by arrival
How late Southwest on BWI to SFO runs when it is late
The 175 late arrivals split 52 under half an hour, 74 between 30 and 60 minutes, and 49 an hour or more.
- 15+ min early40 flights11.1%
- Within 15 min145 flights40.3%
- 15–29 min late52 flights14.4%
- 30–59 min late74 flights20.6%
- 1–2 hours late36 flights10.0%
- 2+ hours late13 flights3.6%
Scale runs 0% to 100%.
Share of 360 completed flights by arrival against schedule.
37 of 186 late departures made up the time and arrived on time, 20% of them. In the other direction, 26 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at SFO.
The worst days
Worst days for Southwest on BWI to SFO
The latest arrival of the period was on 4 June 2026, 3 hours 55 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). On three of the five worst days the largest share was filed as a late-arriving aircraft.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 4 June 2026 | 3 hours 55 minutes | Carrier |
| 10 June 2026 | 3 hours 42 minutes | Late-arriving aircraft |
| 20 May 2026 | 3 hours 37 minutes | Late-arriving aircraft |
| 17 October 2025 | 3 hours 28 minutes | Carrier |
| 5 January 2026 | 3 hours 28 minutes | Late-arriving aircraft |
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 9,600 reported delay minutes.
- 36%Carrier
- 32%National Airspace System
- 30%Late-arriving aircraft
- 2%Extreme weather
32% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 3,079 minutes out of 9,600, against a national NAS share of 21%. The split is drawn from 9,600 reported delay minutes.
The largest share of delay minutes, 36%, falls under carrier control: crew scheduling, maintenance, fuelling, baggage. It accounts for 3,486 of the 9,600 delay minutes reported here.
Cancellations are rare at 0.82%, below the national 1.89% 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
13.6% of arrivals land a full hour or more behind schedule, against 8.3% nationally. Ninety minutes is the honest minimum for a connection 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 63.0% on time across 365 flights, 12 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 12 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 51.4% 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 SFO77.9%
- Southwest Airlines network-wide record
- Baltimore/Washington International Thurgood Marshall (BWI) delay statistics
- San Francisco International (SFO) delay statistics
- The best time of day to fly, according to 7.05 million flight records
- How often a connection fails at the major US hubs
Source: US DOT Bureau of Transportation Statistics, on-time performance data, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.