Carrier route record
WNSFO→BWI
Southwest Airlines · San Francisco to Baltimore
- 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 SFO to BWI draws a D+. Roughly one flight in three arrives at least 15 minutes late, and the typical late arrival is about 50 minutes behind schedule. Build slack into anything you connect to. That rests on 365 flights, with a median arrival 2 minutes late.
The national on-time rate over the same period is 77.3%, so Southwest on SFO to BWI runs 14 points behind the country as a whole. Across a thousand flights that is about 143 extra late arrivals.
Key figures
On time
63.0%
Arrivals under 15 minutes late, of 362 completed flights
Avg delay
50 min
Across delayed arrivals only, not all flights
Cancelled
0.82%
National rate is 1.89%
Whole route
81.0%
Every carrier on SFO to BWI, 1,034 flights
These figures cover 365 flights between September 2025 and August 2026. Beyond the headline rate, 11.0% of arrivals land a full hour or more behind schedule, against 8.3% nationally.
Fare search by Aviasales, a Travelpayouts partner. Booking through it may earn this site a commission at no cost to you; it changes no figure here.
Carrier by carrier
Southwest against every carrier on SFO to BWI
Southwest flew 365 of the 1,034 flights on SFO to BWI, about 35% of it. Its 63.0% on time is 18 points worse than the route as a whole, which runs 81.0%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from United at 90.8% to Southwest at 63.0%.
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 | 669 | 90.8% | 46 min | 0.45% | A+ |
| Southwest Airlines (this page) | 365 | 63.0% | 50 min | 0.82% | D+ |
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 is the single lever a traveller controls, and it moves the odds more than most people expect. Each bar below is the on-time rate for flights scheduled to leave inside that window, across 365 flights.
The overnight block holds up unusually well at 63.0% on time across 365 flights. Red-eyes fly into empty airspace and empty gates, and they are the first rotation of the aircraft's day rather than the last. The 8pm–5am window is the busiest, with 365 flights scheduled in it.
Across the year
Southwest on SFO to BWI through the year
June is the worst month at 26.7% on time, 64 points below March, the best at 90.3%. 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. March was the busiest month here, with 31 flights.
Across the week, Tuesday is the strongest day at 82.7% on time and Thursday the weakest at 46.2%, a spread of 37 points.
Arrival by arrival
How late Southwest on SFO to BWI runs when it is late
The 134 late arrivals split 52 under half an hour, 42 between 30 and 60 minutes, and 40 an hour or more.
- 15+ min early72 flights19.9%
- Within 15 min156 flights43.1%
- 15–29 min late52 flights14.4%
- 30–59 min late42 flights11.6%
- 1–2 hours late34 flights9.4%
- 2+ hours late6 flights1.7%
Scale runs 0% to 100%.
Share of 362 completed flights by arrival against schedule.
33 of 158 late departures made up the time and arrived on time, 21% of them. 9 flights left on time and still arrived late.
The worst days
Worst days for Southwest on SFO to BWI
The latest arrival of the period was on 21 December 2025, 3 hours 9 minutes behind schedule; most of its delay minutes were filed as a late-arriving aircraft. The same cause led on five of the five worst days.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 21 December 2025 | 3 hours 9 minutes | Late-arriving aircraft |
| 3 January 2026 | 3 hours 2 minutes | Late-arriving aircraft |
| 10 November 2025 | 2 hours 15 minutes | Late-arriving aircraft |
| 3 July 2026 | 2 hours 7 minutes | Late-arriving aircraft |
| 14 August 2026 | 2 hours 6 minutes | Late-arriving aircraft |
Delay causes
Why Southwest runs late on this route
Late-arriving aircraft accounts for 85% of the 6,673 delay minutes carriers reported here, and the remaining four split what is left.
- 85%Late-arriving aircraft
- 10%Carrier
- 5%National Airspace System
85% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 6,673 reported delay minutes here, that single category outweighs weather by 85 to one. The split is drawn from 6,673 reported delay minutes.
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
11.0% 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 51.4% on time across 365 flights, 12 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 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 SFO to BWI
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 63.0% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 362 completed flights over 12 months sit behind that.
Related
Where to go next
- SFO to BWI, every carrier
- Southwest on BWI to SFO, the return leg
- United Airlines on SFO to BWI90.8%
- Southwest Airlines network-wide record
- San Francisco International (SFO) delay statistics
- Baltimore/Washington International Thurgood Marshall (BWI) delay statistics
- Why the first flight of the morning is statistically safest
- 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.