Best Time to Fly IAD to SJU: On-Time Stats by Hour & Airline
Washington Dulles International → Luis Munoz Marin International
Data through July 2026 · Last updated October 18, 2026
707 flights were scheduled from Washington (IAD) to San Juan (SJU) in the last 12 months, and 75.8% of those that flew arrived on time, 1.8 points below the US average of 77.6%.
United Airlines was the most punctual of the 2 airlines on the route at 78.7%, while Frontier Airlines trailed at 51.4%.
April has been the best month (90% on time) and Sunday the weakest day of the week (72%).
0.6% of flights were cancelled, versus 1.8% nationally.
IAD to SJU on-time performance by airline
Last 12 months. Airlines with fewer than 30 completed flights are marked “limited data”.
| Airline | On time | Avg delay when late | Cancelled | Flights |
|---|---|---|---|---|
| United Airlines | 78.7% | 53 min | 0.5% | 632 |
| Frontier Airlines | 51.4% | 168 min | 1.3% | 75 |
80%+ good 70–79.9% fair <70% poor
Best time of day to fly IAD to SJU
On-time arrival % by scheduled departure hour (local time), 1,220 flights over 24 months.
Show the numbers
| Departure hour | On time | Cancelled | Flights |
|---|---|---|---|
| 8am–9am | 85.4% | 0.5% | 666 |
| 9am–10am | Limited data | 29 | |
| 10am–11am | Limited data | 5 | |
| 11am–12pm | Limited data | 9 | |
| 12pm–1pm | 25.0% | 2.7% | 37 |
| 4pm–5pm | Limited data | 2 | |
| 5pm–6pm | 71.1% | 0.2% | 421 |
| 7pm–8pm | Limited data | 14 | |
| 8pm–9pm | 43.3% | 3.2% | 31 |
| 9pm–10pm | Limited data | 6 | |
Best day of the week
24 months, by day of departure.
Best month to fly
24 months, by calendar month.
Holiday travel on IAD to SJU
On-time arrivals during holiday periods compared with all other days, last 24 months.
| Period | On time | vs other days | Cancelled | Flights |
|---|---|---|---|---|
| Thanksgiving week (Tue before to Mon after) | Limited data | 26 | ||
| Christmas & New Year (Dec 20 - Jan 3) | 63.8% | -17.6 pts | 2.8% | 71 |
| Summer peak (Jun 15 - Aug 15) | 65.1% | -16.2 pts | 0.5% | 219 |
| All other days | 81.3% | — | 0.3% | 904 |
Monthly on-time trend
On-time arrival % each month, with the 12-month US average for reference.
What causes delays on this route
Share of reported delay minutes, last 12 months (BTS cause categories).