Route profile
IAD→SJU
Flight reliability, delays and best times to fly from Washington to San Juan, 1,571 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 65% of comparable major US routes (4,598 compared)
Calculated from 1,683 flights. How this is calculated · What counts as on time
IAD → SJU arrives on time 80.1% of the time; the return trip, SJU → IAD, arrives on time 85.8% of the time, a 5.7-point gap between the two directions of the same city pair.
IAD → SJU spends 27.4 minutes on the ground on a 1,571-mile trip: 23.0 minutes from pushback to wheels-up at IAD and 4.4 minutes from touchdown to gate at SJU.
Source: US DOT Bureau of Transportation Statistics · Data covering July 2023 – July 2026
What stands out
Reliability here swings unusually widely by season, a wider month-to-month spread than 97% of 3,357 comparable routes.
92.0% on time in a typical April, against 64.4% in July.
Source: FlyerIntel analysis of US DOT BTS data · July 2023 – July 2026 · Ranked against every other route with the same kind of figure and at least 3,357 in the comparison.
What sets this route apart
Where IAD to SJU differs most from similar routes by hour, weekday, month and airline, July 2023 – July 2026.
IAD to SJU holds up on Wednesdays better than routes of similar length do: 87.7% on time to their 80.2%, a 7.5 points lead. Against all other routes the gap is 6.9 points.
May is kinder to IAD to SJU than to routes of similar length: 91.7% on time against 74.8%, 16.9 points better. Against all other routes the gap is 16.5 points.
In December, IAD to SJU runs 6.5 points below routes of similar length, 72.9% on time to 79.4%.
IAD to SJU against comparable routes
July 2023 – July 2026| Measure | This route | Compared with | Them | Gap | Flights behind it |
|---|---|---|---|---|---|
| Weekday: Wednesday | 87.7% | routes of similar length | 80.2% | +7.5 pts | 204 here, 223,863 there |
| Month: May | 91.7% | routes of similar length | 74.8% | +16.9 pts | 133 here, 137,041 there |
| Month: December | 72.9% | routes of similar length | 79.4% | −6.5 pts | 170 here, 129,445 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 1,571 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.
When it goes wrong
July 2023 – July 2026
38 min late
against a median of 7 min early
Percentiles over 1,683 operations; cancelled and diverted flights are counted separately.
Will your connection be tight enough?
Layovers at SJU after arriving from IAD.
| Connection time | Chance of missing | Reads as |
|---|---|---|
| 30 min | 36% | Likely to miss |
| 45 min | 19% | High risk |
| 60 min | 12% | Some risk |
| 90 min | 5.9% | Some risk |
| 120 min | 3.7% | Low 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 0.53% of the time and diverts 0.18% of the time, which a late arrival never shows up in.
Chance of missing is the share of 1,671 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 38 minutes late (90th-percentile gate arrival delay), over 1,683 operations.
Any other layover length: connection checker.
Why IAD → SJU 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 → SJU. 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 | 1,579 | 82.5% | 0.44% | -7 min | 4.8% |
Flights on this route
Flight numbers with at least 600 operations here and still on the schedule.
| Flight | Scheduled | Operations | On time |
|---|---|---|---|
| UA2021 United Airlines | 8:35 AM | 1,074 | 87.4% |
Weekly and seasonal patterns
By day of week
Wednesday is historically the most reliable day and Sunday the least, a gap of 11.2 percentage points.
By month
- Jan: 75.3%
- Feb: 79.6%
- Mar: 85.0%
- Apr: 92.0%
- May: 91.7%
- Jun: 82.0%
- Jul: 64.4%
- Aug: 77.9%
- Sep to Oct: no data
- Nov: 79.5%
- Dec: 72.9%
July is historically the weakest month and April the strongest, a spread of 27.6 percentage points.
Reliability over time
July 2023 – July 2026
Over the most recent 12 months (2025-08 to 2026-07), on-time arrivals averaged 75.8% against 79.0% in the 12 months before — declining by 3.2 percentage points.
Data and methodology
Calculated by FlyerIntel from 1,683 IAD → SJU 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