Route profile
IAD→BOS
Flight reliability, delays and best times to fly from Washington to Boston, 413 miles.
Right now
Aviation weather is not currently a factor.
Aviation weather is not currently a factor.
Route reliability
July 2023 – July 2026
Better than 30% of comparable major US routes (4,598 compared)
Calculated from 4,651 flights. How this is calculated · What counts as on time
IAD → BOS arrives on time 77.5% of the time; the return trip, BOS → IAD, arrives on time 83.4% of the time, a 5.9-point gap between the two directions of the same city pair.
IAD → BOS spends 29.0 minutes on the ground on a 413-mile trip: 22.9 minutes from pushback to wheels-up at IAD and 6.1 minutes from touchdown to gate at BOS.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
What sets this route apart
Where IAD to BOS differs most from similar routes by hour, weekday, month and airline, July 2023 – July 2026.
IAD to BOS is at its best against routes of similar length for flights scheduled at 10 PM: 77.8% arrive on time, 10.7 points ahead of the 67.1% those routes manage at that hour. Against all other routes the gap is 6.2 points.
IAD to BOS struggles most at 5 PM: 62.5% of its flights scheduled then arrive on time, 7.4 points behind the 69.9% on routes of similar length at the same hour. Against all other routes the gap is 7.3 points.
Wednesday is the day IAD to BOS slips furthest against routes of similar length, 78.2% on time where they average 82.0%, 3.8 points lower.
In September, IAD to BOS runs 17 points below routes of similar length, 65.3% on time to 82.3%. Against all other routes the gap is 17.1 points.
February is kinder to IAD to BOS than to routes of similar length: 88.4% on time against 81.5%, 6.9 points better. Against all other routes the gap is 7 points.
IAD to BOS against comparable routes
July 2023 – July 2026| Measure | This route | Compared with | Them | Gap | Flights behind it |
|---|---|---|---|---|---|
| Hour: 10 PM departures | 77.8% | routes of similar length | 67.1% | +10.7 pts | 1,100 here, 32,774 there |
| Hour: 5 PM departures | 62.5% | routes of similar length | 69.9% | −7.4 pts | 1,102 here, 101,189 there |
| Weekday: Wednesday | 78.2% | routes of similar length | 82.0% | −3.8 pts | 657 here, 206,565 there |
| Month: September | 65.3% | routes of similar length | 82.3% | −17.0 pts | 372 here, 122,636 there |
| Month: February | 88.4% | routes of similar length | 81.5% | +6.9 pts | 319 here, 103,821 there |
Each comparison pools the flights of other routes, with this route’s own left out. Similar length means within 15% of this route’s 413 miles, with at least 5 such routes. A bucket is set against the most comparable group that has enough flights: similar length, then the same origin (at least 3 routes), then all other routes. Hours, weekdays and months appear only where both sides have 120 completed flights, and airlines where both have 600. The gap must be at least 2 points and 2 standard errors, and only the largest gap each way is kept per measure. These are differences in the flights counted, not causes.
Why IAD → BOS flights are cancelled
July 2023 – July 2026
IAD → BOS cancelled 78 of 4,651 scheduled flights — about 1 in every 60. The reason filed most often was extreme weather, 66.7% of the cancellations coded on this route — about 1 in every 89 scheduled flights.
Share of cancellations
Of 78 cancelled departures carrying a reason code.
What each reason means
Conditions the carrier judged severe enough to stop the flight: a blizzard, a hurricane, a line of thunderstorms.
52 cancellations, 66.7% of the total.
Crew, maintenance, aircraft cleaning, baggage or fueling: what BTS counts as within the carrier’s own control.
16 cancellations, 20.5% of the total.
Airport capacity, air traffic control flow programs, heavy traffic and ordinary bad weather. A system decision, not the airline’s.
10 cancellations, 12.8% of the total.
A terminal evacuation, a security breach, screening equipment failure, or screening queues over 29 minutes.
0 cancellations, 0.0% of the total.
Reason codes are the operating airline’s own filing with US DOT, not an independent finding of fault. With only one or two carriers on the route, the split mostly reflects how they file. Ordinary bad weather is filed under air traffic, so weather’s full share is larger than its bar.
78 coded cancellations were recorded on IAD → BOS; the section appears from 50.
When it goes wrong
July 2023 – July 2026
55 min late
against a median of 5 min early
IAD → BOS has an average that understates its risk: a typical arrival is 5 min early, but the worst tenth are 60 minutes worse than that. If the trip has something unmissable at the end of it, the median is the wrong number to plan against.
Percentiles over 4,651 operations; cancelled and diverted flights are counted separately.
Will your connection be tight enough?
Layovers at BOS after arriving from IAD.
| Connection time | Chance of missing | Reads as |
|---|---|---|
| 30 min | 38% | Likely to miss |
| 45 min | 22% | High risk |
| 60 min | 16% | High risk |
| 90 min | 9.0% | Some risk |
| 120 min | 5.4% | Some risk |
This is one leg of a connection. Gate changes and the next flight's own schedule matter too. And a connection can fail before delay is even the question — this route cancels 1.68% of the time and diverts 0.09% of the time, which a late arrival never shows up in.
Chance of missing is the share of 4,569 arrivals on this route that landed later than the connection time less 30 minutes to reach the next gate.
The worst tenth of arrivals on this route land at least 55 minutes late (90th-percentile gate arrival delay), over 4,651 operations.
Any other layover length: connection checker.
Best time to fly
IAD → BOS flights departing 5–9 AM arrived on time 91.8% of the time, against 61.8% for 3–6 PM departures, a gap of 30.0 percentage points.
By departure window
By departure hour
- 12 AM to 7 AM: too few flights to score
- 8 AM: 91.8% on time from 953 flights
- 9 AM: 91.3% on time from 153 flights
- 10 AM to 11 AM: too few flights to score
- 12 PM: 80.2% on time from 1,064 flights
- 1 PM to 4 PM: too few flights to score
- 5 PM: 62.5% on time from 1,126 flights
- 6 PM to 9 PM: too few flights to score
- 10 PM: 77.8% on time from 1,117 flights
- 11 PM: too few flights to score
Departure windows with fewer than 120 flights are not scored.
Why IAD → BOS runs late
July 2023 – July 2026
airspace and airport capacity, including weather-driven flow control
the inbound aircraft was late, so this flight started late
crew, maintenance, boarding and fueling, all within the carrier’s control
weather severe enough to stop this flight specifically
Share of the delay minutes US DOT attributed to each cause for IAD → BOS. Only delays of 15 minutes or more are attributed. What the five causes mean
Airlines on this route
Carriers with at least 200 flights, by the airline that operated each one.
| Carrier | Flights | On time | Cancelled | Median delay | Severe |
|---|---|---|---|---|---|
| United Airlines | 4,585 | 77.5% | 1.53% | -5 min | 9.1% |
Other ways to fly Washington to Boston
Airport pairs in the same two city markets, as the DOT defines them.
IAD → BOS is the most reliable pairing for this journey at 77.5% on time, against 76.0% for DCA → BOS.
Flying to BOS from the Washington area? Compare IAD, DCA, BWI for BOS, with the same test for what counts as a real difference.
Flights on this route
Flight numbers with at least 600 operations here and still on the schedule.
UA641 (8:50 AM) arrived on time 91.7% of the time, 30.0 points more often than UA688 (5:10 PM) at 61.7%.
Weekly and seasonal patterns
By day of week
Saturday is historically the most reliable day and Thursday the least, a gap of 9.6 percentage points.
By month
- Jan: 86.4%
- Feb: 88.4%
- Mar: 82.6%
- Apr: 80.9%
- May: 70.8%
- Jun: 73.0%
- Jul: 69.8%
- Aug: 71.8%
- Sep: 65.3%
- Oct: 83.6%
- Nov: 82.3%
- Dec: 81.8%
September is historically the weakest month and February the strongest, a spread of 23.1 percentage points.
Reliability over time
July 2023 – July 2026
- July 2023: 62.5% from 124 flights
- August 2023: 69.4% from 124 flights
- September 2023: 61.6% from 120 flights
- October 2023: 87.1% from 124 flights
- November 2023: too few flights to score (119)
- December 2023: 87.0% from 124 flights
- January 2024: 82.4% from 124 flights
- February 2024: too few flights to score (115)
- March 2024: 86.3% from 124 flights
- April 2024: 79.8% from 120 flights
- May 2024: 71.5% from 124 flights
- June 2024: 78.3% from 120 flights
- July 2024: 70.7% from 124 flights
- August 2024: 65.6% from 124 flights
- September 2024: 77.5% from 120 flights
- October 2024: 89.5% from 124 flights
- November 2024: too few flights to score (119)
- December 2024: 82.1% from 124 flights
- January 2025: 89.2% from 124 flights
- February 2025: too few flights to score (112)
- March 2025: 81.0% from 126 flights
- April 2025: 81.8% from 154 flights
- May 2025: 61.9% from 155 flights
- June 2025: 62.1% from 145 flights
- July 2025: 70.5% from 124 flights
- August 2025: 79.9% from 134 flights
- September 2025: 57.9% from 142 flights
- October 2025: 74.0% from 124 flights
- November 2025: too few flights to score (119)
- December 2025: 76.2% from 122 flights
- January 2026: too few flights to score (111)
- February 2026: too few flights to score (103)
- March 2026: too few flights to score (119)
- April 2026: 80.8% from 120 flights
- May 2026: 81.3% from 124 flights
- June 2026: 81.2% from 120 flights
- July 2026: 73.8% from 176 flights
Over the most recent 12 months (2025-08 to 2026-07), on-time arrivals averaged 77.5% against 76.9% in the 12 months before — broadly unchanged.
Data and methodology
Calculated by FlyerIntel from 4,651 IAD → BOS flight records from the US DOT Bureau of Transportation Statistics, covering July 2023 – July 2026. Late means 15 or more minutes past scheduled arrival; cancelled and diverted flights are left out of on-time rates.
Full methodology · Data sources · Report a problem
Related research: How Long a Layover Needs to Be · Two Airlines on One Route · Best Time of Day to Fly From Major US Airports
Analysis last recomputed