Route reliability record
BOS→BWI
Boston to Baltimore
- Flights
- 3,551
- Period
- July 2025 to June 2026
- Distance
- 369 mi
- Carriers
- 3
This route lands a B, about a point better than the national rate of 77.6%. About one flight in five arrive 15 minutes late or worse, and those flights are late by a little over an hour on average. That is a workable record, not a spotless one. That rests on 3,551 flights, of which Republic Airways flew 1,086 at 81.9% on time.
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
78.9%
Arrivals under 15 minutes late, of 3,452 completed flights
Avg delay
73 min
Across delayed arrivals only, not all flights
Cancelled
2.70%
National rate is 1.81%
Best carrier
Republic
81.9% on time across 1,086 flights
These figures cover 3,551 flights between July 2025 and June 2026. Beyond the headline rate, 8.0% 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
Which airline is most reliable on BOS to BWI
The two carriers here are closely matched: 4 points separate the best from the worst. At that spread, schedule and price are better tie-breakers than reliability. Sample sizes are shown so you can see which rows are worth weighing.
| Airline | Flights | On time | Avg delay | Cancelled | Grade |
|---|---|---|---|---|---|
| Republic Airways | 1,086 | 81.9% | 76 min | 3.31% | B− |
| Southwest Airlines | 2,370 | 77.8% | 72 min | 2.28% | B |
| Spirit Airlinesthin sample | 95 | 73.0% | 67 min | 6.32% | C− |
Republic Airways cancels 3.3% of what it schedules here, the highest in the table. A cancelled flight never appears in an on-time rate, so read that column alongside the punctuality one rather than after it.
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 45 points, against 4 points between the best and worst carrier. Each bar is the on-time rate for flights scheduled inside that window.
- 5am–8am743 flights94.4%
- 8am–11am681 flights89.8%
- 11am–2pm566 flights85.1%
- 2pm–5pm570 flights75.7%
- 5pm–8pm573 flights63.5%
- 8pm–5am418 flights49.1%
Scale runs 40% to 100%. Rows with fewer than 30 flights show a dash.
The 8pm–5am window is where this operation falls apart: 49.1% on time, against 94.4% 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 5am–8am window is the busiest, with 743 flights scheduled in it.
Across the year
When delays peak on this route
This route's year swings by 19 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.
Delays peak in October, when the on-time rate falls to 69.5%. January is the strongest month at 88.4%. Moving a flexible trip across that boundary buys 19 points. July was the busiest month here, with 364 flights.
Across the week, Wednesday is the strongest day at 86.0% on time and Sunday the weakest at 69.2%. 17 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 53% of the 53,000 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.
- 53%Late-arriving aircraft
- 25%Carrier
- 19%National Airspace System
- 4%Extreme weather
- 0%Security
53% 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 53,000 reported delay minutes here, that single category outweighs weather by 14 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 52,901 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 94.4% on time here.
Cancellations run at 2.70%, against 1.81% nationally. That is about one flight in 40 cancelled outright. A cancelled flight is invisible in every on-time figure on this page, so the punctuality numbers above describe only the flights that actually operated.
Connections and stage length
What a delay here actually costs
8.0% 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 are the a little over an hour kind, which a normal layover absorbs.
At 369 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 5am–8am window matters as much as it does.
The return leg is a different operation and performs like one: it runs 74.8% on time across 3,556 flights, 4 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 4 points of difference.
The sample behind these figures is 3,551 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 this route
Put together: the calendar is the biggest lever here, not the carrier or the hour. January runs 88.4% on time and October 69.5%, a swing of 19 points. If the dates move at all, move them out of October before you think about anything else. 3,452 completed flights over 12 months sit behind that.
Common questions
BOS to BWI questions
How often is BOS to BWI delayed?
About one flight in five arrive at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 21.1% of the 3,551 flights in this analysis, against 22.4% nationally. Delayed flights are late by a little over an hour on average.
Which airline is most reliable on BOS to BWI?
Republic Airways leads at 81.9% on time across 1,086 flights. Southwest Airlines is at the other end on 77.8%, a gap of 4 points. Sample size matters as much as the percentage: a rate built from a few hundred flights moves around far more than one built from ten thousand.
What time of day has the fewest delays on BOS to BWI?
The 5am–8am departure window is the strongest at 94.4% on time. The 8pm–5am window is the weakest at 49.1%, 45 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 October delays on BOS to BWI?
October is the weakest month at 69.5% on time, compared with 88.4% in January. Across the year that is 19 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
- BWI to BOS — the return legseparate record
- Boston Logan International (BOS) delay statistics
- Baltimore/Washington International Thurgood Marshall (BWI) delay statistics
- Republic Airways on-time record81.9%
- Southwest Airlines on-time record77.8%
- Spirit Airlines on-time record73.0%
- Why the first flight of the morning is statistically safest
- What a cancellation rate actually tells you (and what it hides)
Direction matters. BOS to BWI and BWI to BOS are scored separately because they are separate operations, with different departure banks and different aircraft. Compare the return leg.
Source: US DOT Bureau of Transportation Statistics, on-time performance data, July 2025 to June 2026. Updated monthly. How this data is collected.