Carrier route record
WNBWI→MIA
Southwest Airlines · Baltimore to Miami
- Flights
- 1,189
- Period
- September 2025 to August 2026
- Share of route
- 52%
- Carriers
- 5
Historical statistics for September 2025 to August 2026, not live status. For today’s flights, check with Southwest Airlines.
Southwest on BWI to MIA sits in the middle of the pack with a C. About seven flights in ten arrive on time by the DOT's definition, 5 points worse than the national rate of 77.3%. The late ones land roughly 55 minutes behind schedule. That rests on 1,189 flights, with a median arrival right on schedule.
The national on-time rate over the same period is 77.3%, so Southwest on BWI to MIA runs 5 points behind the country as a whole. Across a thousand flights that is about 47 extra late arrivals.
Key figures
On time
72.6%
Arrivals under 15 minutes late, of 1,159 completed flights
Avg delay
53 min
Across delayed arrivals only, not all flights
Cancelled
2.27%
National rate is 1.89%
Whole route
75.3%
Every carrier on BWI to MIA, 2,294 flights
These figures cover 1,189 flights between September 2025 and August 2026. On-time means an arrival less than 15 minutes after the scheduled gate time, the same threshold the Department of Transportation uses in its own reports. Cancelled and diverted flights are excluded from the on-time rate and counted separately, which is why the cancellation column matters on its own.
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 BWI to MIA
Southwest flew 1,189 of the 2,294 flights on BWI to MIA, most of the route. Its 72.6% on time is 3 points worse than the route as a whole, which runs 75.3%. Ranked by on-time rate it is number three of five carriers on the route, where the range runs from Envoy at 81.8% to Spirit at 60.0%. Three 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 |
|---|---|---|---|---|---|
| Envoy Airthin sample | 121 | 81.8% | 64 min | 0.00% | B+ |
| American Airlines | 699 | 80.6% | 117 min | 2.29% | B |
| Southwest Airlines (this page) | 1,189 | 72.6% | 53 min | 2.27% | C |
| Frontier Airlinesthin sample | 269 | 71.1% | 87 min | 4.46% | C− |
| Spirit Airlinesthin sample | 16 | 60.0% | 46 min | 6.25% | 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 matters more here than the choice of carrier. The gap between the best and worst window is 33 points, against half a point between the best and worst carrier.
- 5am–8am64 flights89.1%
- 8am–11am330 flights80.0%
- 11am–2pm295 flights77.5%
- 2pm–5pm130 flights61.1%
- 5pm–8pm194 flights69.1%
- 8pm–5am176 flights56.3%
Scale runs 50% to 95%.
The 8pm–5am window is where this operation falls apart: 56.3% on time, against 89.1% for the 5am–8am 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 330 flights scheduled in it.
Across the year
Southwest on BWI to MIA through the year
December is the weak month at 63.5% on time, against 87.0% in September. Winter delays cluster: a single storm system can account for most of a month's shortfall, so an average December hides both very good weeks and genuinely unflyable days. December was the busiest month here, with 106 flights.
Across the week, Tuesday is the strongest day at 82.2% on time and Sunday the weakest at 62.3%, a spread of 20 points.
Arrival by arrival
How late Southwest on BWI to MIA runs when it is late
The 317 late arrivals split 142 under half an hour, 92 between 30 and 60 minutes, and 83 an hour or more.
- 15+ min early216 flights18.6%
- Within 15 min626 flights54.0%
- 15–29 min late142 flights12.3%
- 30–59 min late92 flights7.9%
- 1–2 hours late56 flights4.8%
- 2+ hours late27 flights2.3%
Scale runs 0% to 100%.
Share of 1,159 completed flights by arrival against schedule.
A late pushback is often recovered here: of 339 departures that left 15 minutes late or more, 104 still arrived on time. In the other direction, 82 flights left on time yet arrived 15 minutes late or more, so that delay built up after pushback: in the air, in a holding pattern or on the ground at MIA.
The worst days
Worst days for Southwest on BWI to MIA
The latest arrival of the period was on 4 July 2026, 5 hours 30 minutes behind schedule; most of its delay minutes were filed as carrier-caused (crew, maintenance, fuelling, baggage). The five worst days are spread across July, November, December, June and August, with no single month standing out.
| Date | Arrived late by | Largest filed cause |
|---|---|---|
| 4 July 2026 | 5 hours 30 minutes | Carrier |
| 9 November 2025 | 5 hours 3 minutes | National Airspace System |
| 27 December 2025 | 4 hours 50 minutes | Carrier |
| 10 June 2026 | 4 hours 38 minutes | Late-arriving aircraft |
| 7 August 2026 | 4 hours 35 minutes | Late-arriving aircraft |
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 17,000 reported delay minutes.
- 39%Late-arriving aircraft
- 30%Carrier
- 26%National Airspace System
- 4%Extreme weather
- 1%Security
39% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 17,000 reported delay minutes here, that single category outweighs weather by 10 to one. The split is drawn from 16,705 reported delay minutes.
The practical consequence: the 5am–8am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 89.1% on time here.
Cancellations sit at 2.27% against a national 1.89%, which is ordinary. Diversions add another 0.25%.
Connections and stage length
What a delay here costs
7.2% of arrivals land an hour or more late, close to the national 8.3%, so 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.
The 946 miles between these two airports put this in the middle of the US network, around two and a half to three hours of block time. That is enough cruise to absorb a ten-minute late pushback and not enough to absorb thirty.
The return leg runs 73.6% on time across 1,188 flights, within about a point of this direction. The two legs are scored separately because they usually differ; on this city pair they happen not to.
The sample behind these figures is 1,189 flights, enough that the headline rate is stable to within roughly a point. The hour-block and month splits divide that further, so read the thinner bars with more caution than the headline.
What to do with this
Booking Southwest on BWI to MIA
Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 87.0% on time and December 63.5%, a swing of 24 points. If the dates move at all, move them out of December before you think about anything else. 1,159 completed flights over 12 months sit behind that.
Related
Where to go next
- BWI to MIA, every carrier
- Southwest on MIA to BWI, the return leg
- Envoy Air on BWI to MIA81.8%
- American Airlines on BWI to MIA80.6%
- Frontier Airlines on BWI to MIA71.1%
- Southwest Airlines network-wide record
- Baltimore/Washington International Thurgood Marshall (BWI) delay statistics
- Miami International (MIA) delay statistics
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.05 million flight records
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.