Altius recorded 308 priced readings of nonstop business-class round trips from Washington (IAD) to Lisbon (LIS) booked 90 days out, across 139 departure dates between 2026-05-20 and 2026-10-05. Observed fares ran from US$3,299 to US$8,538. The lowest fare Altius scored on this window was US$3,299 for a 2026-12-07 departure, seen on 2026-09-08 — RARE at the time, 42.8% below the US$5,767 this route was typically running that day.
A fare can move between our two readings of the same day, most often on the days furthest below typical. Where a day's two readings differ enough to matter, the chart marks that day and both readings can be read separately.