Route reliability record
BOS→IAD
Boston to Washington
- Flights
- 1,527
- Period
- September 2025 to August 2026
- Distance
- 412 mi
- Carriers
- 2
This route lands a B−, 6 points better than the national rate of 77.3%. About one flight in six arrives 15 minutes late or worse, and those flights are late by an hour and a half on average. That rests on 1,527 BOS to IAD flights, with a median arrival 8 minutes early.
Best time to fly BOS to IAD: a 5am–8am departure, ideally on a Saturday. Flights in that window arrived on time 96.2% of the time and Saturday flights 87.5%, against 83.2% for the route overall.
Set against the rest of the country, this route's record is 6 points better than the US average of 77.3%. That gap is worth roughly 59 fewer late arrivals for every thousand flights.
Key figures
On time
83.2%
Arrivals under 15 minutes late, of 1,480 completed flights
Avg delay
85 min
Across delayed arrivals only, not all flights
Cancelled
3.01%
National rate is 1.89%
Best carrier
United
83.3% on time across 1,450 flights
These figures cover 1,527 flights between September 2025 and August 2026. The median arrival is 8 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.
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Carrier by carrier
Which airline is most reliable on BOS to IAD
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 |
|---|---|---|---|---|---|
| United Airlines | 1,450 | 83.3% | 78 min | 2.28% | B |
| Republic Airwaysthin sample | 77 | 79.7% | 208 min | 16.88% | B− |
Flight by flight
Flights on BOS to IAD
The flight numbers below flew this route at least 250 times in the period, busiest first. Each has its own record, with its schedule and delay causes.
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Best ways to make this trip
The most reliable ways to fly Boston to Washington
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. 4 of the top 5 use a different airport at one end.
| Option | Airline | Success | On time | Cancelled | Best departure | Most punctual flight |
|---|---|---|---|---|---|---|
| 1. MHT → BWIManchester to Baltimore | Southwest Airlines | 87.7% | 88.4% | 0.76% | 5am–8am, Wed | — |
| 2. PVD → BWIProvidence to Baltimore | Southwest Airlines | 85.2% | 86.9% | 1.95% | 5am–8am, Wed | — |
| 3. BOS → IADBoston to Washington | United Airlines | 81.4% | 83.3% | 2.28% | 5am–8am, Sat (route) | UA 1734 05:45 |
| 4. BOS → BWIBoston to Baltimore | Republic Airways | 78.3% | 81.8% | 4.28% | 5am–8am, Thu | YX 5644 17:25 |
| 5. PVD → DCAProvidence to Washington | Southwest Airlines | 75.2% | 76.8% | 2.09% | 5am–8am, Wed | — |
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 26 points, against half a point between the best and worst carrier.
- 5am–8am346 flights96.2%
- 8am–11am365 flights89.7%
- 11am–2pm61 flights91.5%
- 2pm–5pm364 flights76.5%
- 5pm–8pm391 flights70.2%
- 8pm–5am—
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 96.2% of the time, against 70.2% for the evening window. That is 26 points of difference for no extra money, and it comes from the same aircraft having had no earlier flight to fall behind on. The 5pm–8pm window is the busiest, with 391 flights scheduled in it.
Explore
Filter BOS to IAD by airline, time, month and day
Pick a breakdown and a carrier. The dashed mark on each row is the same slice for every US flight.
On BOS to IAD, the best departure window is 5am–8am at 96.2% on time and the worst is 5pm–8pm at 70.2%, a wide gap of 26.0 points. All US flights leaving 5am–8am ran 89.3%.
- 5–8am96.2%
- 8–11am89.7%
- 11am–2pm91.5%
- 2–5pm76.5%
- 5–8pm70.2%
- 8pm–5am—
best all US flightsScale 60% to 100%. Cells under 30 flights show a dash.
Across the year
When delays peak on this route
This route's year swings by 16 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.
May is the best month on the calendar at 89.3% on time. Shoulder season thins the schedule and takes the summer weather with it, and the operation gets its margin back. July was the busiest month here, with 176 flights.
Across the week, Saturday is the strongest day at 87.5% on time and Sunday the weakest at 79.3%, a spread of 8 points.
Delay causes
Why this route gets delayed
Late-arriving aircraft accounts for 44% of the 21,000 delay minutes carriers reported here, and the remaining four split what is left.
- 44%Late-arriving aircraft
- 36%National Airspace System
- 17%Carrier
- 2%Extreme weather
44% of delay minutes trace back to a late-arriving aircraft, meaning the plane was already behind before it got here. Across 21,000 reported delay minutes here, that single category outweighs weather by 18 to one. The split is drawn from 21,042 reported delay minutes.
36% of delay minutes are charged to the National Airspace System: air traffic volume, runway configuration, ground stops. No carrier can price its way out of that, which is why airport choice moves the number here more than carrier choice does. That is 7,584 minutes out of 21,000, against a national NAS share of 21%.
Cancellations run at 3.01%, against 1.89% nationally. That is roughly one flight in 30 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
6.9% 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 an hour and a half, which a normal layover absorbs.
At 412 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 76.9% on time across 1,524 flights, 6 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 6 points of difference.
The sample behind these figures is 1,527 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 IAD after this flight
What to do with this
Booking this route
Put together: the delay figures matter less here than the 3.01% cancellation rate. A late arrival costs you an hour and a half; a cancelled flight costs you the day. Book the 5am–8am departure so there is still a schedule behind you if it goes wrong, and treat a same-day connection as optimistic. 1,480 completed flights over 12 months sit behind that.
Common questions
BOS to IAD questions
How often is BOS to IAD delayed?
About one flight in six arrives at least 15 minutes late, which is the Department of Transportation's definition of a delayed arrival. That works out to 16.8% of the 1,527 flights in this analysis, against 22.7% nationally. Delayed flights are late by an hour and a half on average.
How reliable is BOS to IAD compared with the rest of the country?
83.2% of flights arrive on time here against a national 77.3%, a difference of 6 points in its favour. That is worth a B− on this site's grading scale.
What time of day has the fewest delays on BOS to IAD?
The 5am–8am departure window is the strongest at 96.2% on time. The 5pm–8pm window is the weakest at 70.2%, 26 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 IAD?
October is the weakest month at 73.2% on time, compared with 89.3% in May. Across the year that is 16 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
- IAD to BOS — the return legseparate record
- Boston Logan International (BOS) delay statistics
- Washington Dulles International (IAD) delay statistics
- BOS to DCA, a related route72.6%
- ATL to IAD, a related route76.4%
- BOS to ORD, a related route71.9%
- United Airlines on-time record83.3%
- Republic Airways on-time record79.7%
- The US routes with the most cancellations
- Why the first flight of the morning is statistically safest
Direction matters. BOS to IAD and IAD to BOS 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, September 2025 to August 2026. Last updated ; recomputed monthly. How this data is collected.