Carrier route record
WNBWI→SLC
Southwest Airlines · Baltimore to Salt Lake City
- 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 BWI to SLC sits in the middle of the pack with a C. Close to three flights in four arrive on time by the DOT's definition, 3 points worse than the national rate of 77.6%. The late ones land roughly 55 minutes behind schedule. That rests on 410 flights, with a median arrival 1 minute late.
The US average over the same twelve months is 77.6%, so there is little to separate Southwest on BWI to SLC from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
74.2%
Arrivals under 15 minutes late, of 403 completed flights
Avg delay
53 min
Across delayed arrivals only, not all flights
Cancelled
1.46%
National rate is 1.81%
Whole route
77.0%
Every carrier on BWI to SLC, 770 flights
These figures cover 410 flights between July 2025 and June 2026. Beyond the headline rate, 8.2% 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 BWI to SLC
Southwest flew 410 of the 770 flights on BWI to SLC, most of the route. Its 74.2% on time is 3 points worse than the route as a whole, which runs 77.0%. Ranked by on-time rate it is last of two carriers on the route, where the range runs from Delta at 80.2% to Southwest at 74.2%. 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.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Delta Air Linesthin sample | 360 | 80.2% | 59 min | 1.67% | B |
| Southwest Airlines (this page) | 410 | 74.2% | 53 min | 1.46% | C |
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 25 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–8am13 flights—
- 8am–11am149 flights82.2%
- 11am–2pm91 flights76.4%
- 2pm–5pm51 flights74.5%
- 5pm–8pm68 flights58.2%
- 8pm–5am38 flights56.8%
Scale runs 50% to 90%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 56.8% on time, against 82.2% 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 149 flights scheduled in it.
Across the year
Southwest on BWI to SLC through the year
Delays peak in March, when the on-time rate falls to 45.9%. August is the strongest month at 87.5%. Moving a flexible trip across that boundary buys 42 points. February was the busiest month here, with 50 flights.
Across the week, Monday is the strongest day at 83.6% on time and Saturday the weakest at 64.9%. 19 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. Carrier accounts for 46% of the 5,483 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.
- 46%Carrier
- 27%Late-arriving aircraft
- 21%National Airspace System
- 5%Extreme weather
- 1%Security
The largest share of delay minutes, 46%, 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 2,549 of the 5,483 delay minutes reported here. The split is drawn from 5,483 reported delay minutes.
Cancellations sit at 1.46% against a national 1.81%, which is ordinary. Diversions add another 0.24%.
Connections and stage length
What a delay here costs
8.2% 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 55 minutes, which a normal layover absorbs.
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 82.6% on time across 410 flights, 8 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 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 BWI to SLC
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 74.2% headline is the most reliable number on the page; the hour and month splits below it are built on a few dozen flights each. 403 completed flights over 12 months sit behind that.
Related
Where to go next
- BWI to SLC, every carrier
- Southwest on SLC to BWI, the return leg
- Delta Air Lines on BWI to SLC80.2%
- Southwest Airlines network-wide record
- Baltimore/Washington International Thurgood Marshall (BWI) delay statistics
- Salt Lake City International (SLC) delay statistics
- The best time of day to fly, according to 7.04 million flight records
- Connecting flights: how much buffer the data says you need
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.