Carrier route record

WNBNA→SFO

Southwest Airlines · Nashville to San Francisco

Flights: 311
Period: July 2025 to June 2026
Share of route: 27%
Carriers: 2

Historical statistics for July 2025 to June 2026, not live status. For today’s flights, check with Southwest Airlines.

Southwest on BNA to SFO earns a D+, which is as low as this site's scale goes for a reason. Only 55.2% of flights arrive inside the 15-minute window, 22 points worse than the national rate of 77.6%. Late arrivals average about 55 minutes. Treat any tight connection here as a coin flip. That rests on 311 flights, with a median arrival 12 minutes late.

The national on-time rate over the same period is 77.6%, so Southwest on BNA to SFO runs 22 points behind the country as a whole. Across a thousand flights that is about 224 extra late arrivals.

On time

55.2%

Arrivals under 15 minutes late, of 308 completed flights

Avg delay

55 min

Across delayed arrivals only, not all flights

Cancelled

0.64%

National rate is 1.81%

Whole route

70.6%

Every carrier on BNA to SFO, 1,162 flights

These figures cover 311 flights between July 2025 and June 2026. Beyond the headline rate, 15.3% 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 BNA to SFO

Southwest flew 311 of the 1,162 flights on BNA to SFO, about 27% of it. Its 55.2% on time is 15 points worse than the route as a whole, which runs 70.6%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from United at 76.3% to Southwest at 55.2%.

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.

On-time performance by carrier on BNA to SFO
Airline	Flights	On time	Avg delay	Cancelled	Grade
United Airlines	851	76.3%	60 min	0.82%	B+
Southwest Airlines (this page)thin sample	311	55.2%	55 min	0.64%	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 35 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–11am12 flights—
11am–2pm122 flights69.2%
2pm–5pm94 flights52.1%
5pm–8pm82 flights34.1%
8pm–5am1 flights—

Scale runs 25% to 75%. Rows with fewer than 30 flights show a dash.

The 5pm–8pm window is where this operation falls apart: 34.1% on time, against 69.2% for the 11am–2pm 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 11am–2pm window is the busiest, with 122 flights scheduled in it.

Across the year

Southwest on BNA to SFO through the year

Jul–Sep 202591 flights67.0%
Oct–Dec 202568 flights61.2%
Jan–Mar 202661 flights78.0%
Apr–Jun 202691 flights24.2%

Scale runs 15% to 85%. Rows with fewer than 30 flights show a dash.

Monthly volumes are too low here to break the year into twelve reliable readings. What the twelve-month total says is 55.2% on time across 311 flights.

Southwest on BNA to SFO did not run the same all year. Its best quarter was Jan–Mar 2026 at 78.0% on time and its weakest Apr–Jun 2026 at 24.2%, a swing of 54 points on roughly 78 flights a quarter. The twelve-month rate averages over that, so if you are flying in a weak quarter the quarter's own figure is the better guide.

Across the week, Friday is the strongest day at 66.7% on time and Monday the weakest at 45.5%. 21 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 43% of the 7,544 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
43%
National Airspace System
29%
Carrier
26%
Extreme weather
2%

43% 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 7,544 reported delay minutes here, that single category outweighs weather by 20 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 7,544 reported delay minutes.

Cancellations are rare at 0.64%, 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. 15.3% 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 1,969 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 runs 57.6% on time across 311 flights, within 2 points of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.

One caution: this is a thin sample. 311 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 BNA to SFO

Put together: treat all of this as provisional. 311 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 55.2% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 308 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