Carrier route record

WNSLC→BWI

Southwest Airlines · Salt Lake City to Baltimore

Flights: 410
Period: July 2025 to June 2026
Share of route: 53%
Carriers: 2

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

Southwest on SLC to BWI lands a B, 5 points better than the national rate of 77.6%. About one flight in six arrives 15 minutes late or worse, and those flights are late by about an hour on average. That is a workable record, not a spotless one. That rests on 410 flights, with a median arrival 7 minutes early.

Set against the rest of the country, Southwest's SLC to BWI record is 5 points better than the US average of 77.6%. That gap is worth roughly 50 fewer late arrivals for every thousand flights.

On time

82.6%

Arrivals under 15 minutes late, of 403 completed flights

Avg delay

57 min

Across delayed arrivals only, not all flights

Cancelled

1.22%

National rate is 1.81%

Whole route

80.4%

Every carrier on SLC to BWI, 770 flights

These figures cover 410 flights between July 2025 and June 2026. The median arrival is 7 minutes early, which is the part an average hides: most flights here are fine, and the on-time rate is decided by a tail of badly late ones. On-time means under 15 minutes late, the DOT's own threshold.

Carrier by carrier

Southwest against every carrier on SLC to BWI

Southwest flew 410 of the 770 flights on SLC to BWI, most of the route. Its 82.6% on time is 2 points better than the route as a whole, which runs 80.4%. Ranked by on-time rate it is first of two carriers on the route, where the range runs from Southwest at 82.6% to Delta at 77.9%. One of those carriers flew fewer than 365 flights here, so treat their positions as rough.

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 SLC to BWI
Airline	Flights	On time	Avg delay	Cancelled	Grade
Southwest Airlines (this page)	410	82.6%	57 min	1.22%	B
Delta Air Linesthin sample	360	77.9%	35 min	1.67%	B

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. Each bar is the on-time rate for flights scheduled inside that window.

5am–8am53 flights94.2%
8am–11am35 flights88.6%
11am–2pm131 flights77.2%
2pm–5pm73 flights67.6%
5pm–8pm—
8pm–5am118 flights90.7%

Scale runs 60% to 100%. Rows with fewer than 30 flights show a dash.

Book the early departure. Flights leaving between 5am–8am arrive on time 94.2% of the time, against 67.6% for the afternoon window. That is 27 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 11am–2pm window is the busiest, with 131 flights scheduled in it.

Across the year

Southwest on SLC to BWI through the year

Darker means more delays. Figures are on-time percentages.May best, July worst

July is the worst month at 63.6% on time, 30 points below May, the best at 93.5%. 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. February was the busiest month here, with 50 flights.

Across the week, Tuesday is the strongest day at 90.7% on time and Sunday the weakest at 70.9%. 20 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 4,012 reported delay minutes.

Late-arriving aircraft
42%
Carrier
39%
National Airspace System
15%
Extreme weather
4%
Security
0%

42% 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 4,012 reported delay minutes here, that single category outweighs weather by 12 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 4,012 reported delay minutes.

The largest share of delay minutes, 39%, 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 1,578 of the 4,012 delay minutes reported here.

Cancellations sit at 1.22% against a national 1.81%, which is ordinary. Diversions add another 0.49%.

Connections and stage length

What a delay here costs

Badly late arrivals are rare here: only 4.5% land an hour or more behind schedule, against 8.1% nationally. Connections built on this flight are about as safe as US domestic connections get, though a cancelled flight still ignores every layover you give it.

At 1,865 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 74.2% on time across 410 flights, 8 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 8 points of difference.

One caution: this is a thin sample. 410 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 SLC to BWI

Put together: treat all of this as provisional. 410 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 82.6% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 403 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