Route reliability record
BWI→PWM
Baltimore to Portland
- Flights
- 1,341
- Period
- July 2025 to June 2026
- Distance
- 452 mi
- Carriers
- 1
This route lands a B, 2 points better than the national rate of 77.6%. About one flight in five arrives 15 minutes late or worse, and those flights are late by about 50 minutes on average. That is a workable record, not a spotless one. That rests on 1,341 BWI to PWM flights, with a median arrival 4 minutes early.
Best time to fly BWI to PWM: a 8am–11am departure, ideally on a Wednesday. Flights in that window arrived on time 90.7% of the time and Wednesday flights 82.8%, against 79.2% for the route overall.
The US average over the same twelve months is 77.6%, so there is little to separate this route from the country as a whole. The variation that matters here is internal: which carrier, and what time of day.
Key figures
On time
79.2%
Arrivals under 15 minutes late, of 1,323 completed flights
Avg delay
49 min
Across delayed arrivals only, not all flights
Cancelled
1.34%
National rate is 1.81%
Best carrier
Southwest
79.2% on time across 1,341 flights
These figures cover 1,341 flights between July 2025 and June 2026. The median arrival is 4 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
Which airline is most reliable on BWI to PWM
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 |
|---|---|---|---|---|---|
| Southwest Airlines | 1,341 | 79.2% | 49 min | 1.34% | B |
Best ways to make this trip
The most reliable ways to fly Baltimore to Portland
Every airline on this route and on the routes between nearby airports, ranked by how often a scheduled flight actually operated and arrived on time. 3 of the top 4 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. IAD → PWMWashington to Portland | Republic Airways | 85.8% | 87.9% | 2.37% | 8am–11am, Sat (route) | — |
| 2. BWI → PWMBaltimore to Portland | Southwest Airlines | 78.1% | 79.2% | 1.34% | 8am–11am, Wed | — |
| 3. DCA → PWMWashington to Portland | American Airlines | 68.3% | 69.9% | 2.29% | 8am–11am, Sat | — |
| 4. DCA → PWMWashington to Portland | PSA Airlines | 63.7% | 66.7% | 4.57% | 8am–11am, Sat | — |
Success is the share of scheduled flights that operated and arrived less than 15 minutes late, so a cancelled flight counts against it. “(route)” means the best time comes from every carrier on the route rather than this airline alone.
Departure window
The best time of day to leave
Departure time matters more here than the choice of carrier. The gap between the best and worst window is 24 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–11am377 flights90.7%
- 11am–2pm281 flights85.1%
- 2pm–5pm224 flights77.2%
- 5pm–8pm80 flights69.2%
- 8pm–5am379 flights66.4%
Scale runs 60% to 95%. Rows with fewer than 30 flights show a dash.
Book the morning departure. Flights leaving between 8am–11am arrive on time 90.7% of the time, against 66.4% for the overnight window. That is 24 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 8pm–5am window is the busiest, with 379 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 34 points from best month to worst, which is wide. An annual average tells you very little about the week you are actually flying, so read the strip rather than the headline if your dates are fixed.
July is the worst month at 53.4% on time, 34 points below September, the best at 87.6%. 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. August was the busiest month here, with 135 flights.
Across the week, Wednesday is the strongest day at 82.8% on time and Sunday the weakest at 72.3%. 11 points is a smaller lever than departure hour, but it is free.
Delay causes
Why this route gets delayed
One category carries most of the weight here. Late-arriving aircraft accounts for 51% of the 14,000 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.
- 51%Late-arriving aircraft
- 31%Carrier
- 10%National Airspace System
- 7%Extreme weather
51% 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 14,000 reported delay minutes here, that single category outweighs weather by 7 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 13,543 reported delay minutes.
The practical consequence: the 8am–11am departure is the one that starts clean. Its aircraft has no earlier leg to be late from, which is exactly why that window shows 90.7% on time here.
Cancellations sit at 1.34% against a national 1.81%, which is ordinary. Diversions add another 0.00%.
Connections and stage length
What a delay here actually costs
Badly late arrivals are rare here: only 4.2% 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 452 miles this is a short hop, and stage length matters more than it looks. A flight this short spends under two hours in the air, which leaves almost nothing to claw back a late pushback with. Delay here is decided on the ground, in the turn, which is why the 8am–11am window matters as much as it does.
The return leg runs 81.8% on time across 1,341 flights, within 3 points 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 1,341 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.
Work out the risk of missing a connection in PWM after this flight
What to do with this
Booking this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. September runs 87.6% on time and July 53.4%, a swing of 34 points. If the dates move at all, move them out of July before you think about anything else. 1,323 completed flights over 12 months sit behind that.
Common questions
BWI to PWM questions
How often is BWI to PWM delayed?
About one flight in five arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 20.8% of the 1,341 flights in this analysis, against 22.4% nationally. Delayed flights are late by about 50 minutes on average.
How reliable is BWI to PWM compared with the rest of the country?
79.2% of flights arrive on time here against a national 77.6%, a difference of 2 points in its favour. That is worth a B on this site's grading scale.
What time of day has the fewest delays on BWI to PWM?
The 8am–11am departure window is the strongest at 90.7% on time. The 8pm–5am window is the weakest at 66.4%, 24 points behind. Later departures inherit delays from earlier flights the same aircraft has already flown, which is why the curve slopes the way it does.
How bad are July delays on BWI to PWM?
July is the weakest month at 53.4% on time, compared with 87.6% in September. Across the year that is 34 points between the best and worst months. Moving flexible dates out of that month is one of the few things that reliably helps.
Related
Where to go next
- PWM to BWI — the return legseparate record
- Baltimore/Washington International Thurgood Marshall (BWI) delay statistics
- BWI to ATL, a related route80.6%
- ORD to PWM, a related route74.0%
- BWI to MCO, a related route75.6%
- Southwest Airlines on-time record79.2%
- Why the first flight of the morning is statistically safest
- The best time of day to fly, according to 7.04 million flight records
Direction matters. BWI to PWM and PWM to BWI are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
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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.