Carrier route record

WNSFO→BWI

Southwest Airlines · San Francisco to Baltimore

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 SFO to BWI draws a C+. About one flight in three arrives at least 15 minutes late, and the typical late arrival is roughly 45 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 77.6%, so Southwest on SFO to BWI runs 12 points behind the country as a whole. Across a thousand flights that is about 119 extra late arrivals.

On time

65.7%

Arrivals under 15 minutes late, of 362 completed flights

Avg delay

47 min

Across delayed arrivals only, not all flights

Cancelled

0.82%

National rate is 1.81%

Whole route

81.0%

Every carrier on SFO to BWI, 1,085 flights

These figures cover 365 flights between July 2025 and June 2026. Beyond the headline rate, 8.3% 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 SFO to BWI

Southwest flew 365 of the 1,085 flights on SFO to BWI, about 34% of it. Its 65.7% on time is 15 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 88.7% to Southwest at 65.7%.

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.

On-time performance by carrier on SFO to BWI
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	720	88.7%	49 min	0.42%	A+
Southwest Airlines (this page)	365	65.7%	47 min	0.82%	C+

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 65.7% 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

Darker means more delays. Figures are on-time percentages.March best, June worst

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, Saturday is the strongest day at 82.4% on time and Monday the weakest at 53.8%. 29 points is a smaller lever than departure hour, but it is free.

Delay causes

Why Southwest runs late on this route

One category carries most of the weight here. Late-arriving aircraft accounts for 85% of the 5,775 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.

Late-arriving aircraft
85%
Carrier
9%
National Airspace System
6%

85% 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 5,775 reported delay minutes here, that single category outweighs weather by 85 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 5,775 reported delay minutes.

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

8.3% 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 roughly 45 minutes, which a normal layover absorbs.

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 57.2% on time across 365 flights, 9 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 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 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 65.7% 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.

Where to go next

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.

Key figures