$108 Cheap United flights Washington (IAD) to San Juan (SJU)

Scoring cheap one-way United Airlines flights from IAD to SJU from $108 on Expedia is a cinch — just filter by "Price (lowest to highest)." Alternatively, check out our affordable return fares from $202 for your next exciting vacation.**These prices were available on Expedia within the past 7 days, for flights departing within the next year. Prices and availability are subject to change. Additional terms apply.

Search for United Airlines flights from IAD to SJU about one month before you want to leave. The cheapest time to reserve an international flight is usually 18 to 29 days ahead of your departure date when you can save 17% versus booking four to five months in advance. No matter your fare class and itinerary, the best day to book international airfare is usually Sunday. Friday can be the most expensive. Passengers who book on a Sunday can save 17% on average compared to those who book on a Friday.**Ideal booking window recommendation is based on average round-trip ticket prices for January through November for 2024. Best day of the week to book recommendation is based on average round-trip ticket prices for January through October 2024. All data sourced from ARC's global airline sales database.

Jetting off from IAD at 8:30AM UTC-5, the first United Airlines flight to SJU arrives at 1:17PM UTC-4. Flying earlier in the day means you're less likely to encounter cancellations or delays.* Not a morning person? The last United Airlines flight from IAD to SJU departs at 5:35PM UTC-5 and touches down at 10:22PM UTC-4.*Most reliable time of the day recommendation is based on January through August 2024 flight status data sourced from OAG's global flight data platform.

A rewarding loyalty program and the ability to rack up points through United Mileage Plus are the start of the reasons to jet off from IAD to SJU with United Airlines. Plus, by joining Expedia's free One Key™ program, you can receive OneKeyCash™* in addition to United Airlines's loyalty program earnings. It's yours to spend on future bookings.*OneKeyCash™ disclaimer - OneKeyCash™ is not redeemable for cash and can only be used on Expedia, Hotels.com and Vrbo.