Altius recorded 312 priced readings of nonstop business-class round trips from Boston (BOS) to Madrid (MAD) booked 90 days out, across 139 departure dates between 2026-05-20 and 2026-10-05. Observed fares ran from US$2,901 to US$16,668. The lowest fare Altius scored on this window was US$2,901 for a 2026-08-19 departure, seen on 2026-05-21 — RARE at the time, 32.3% below the US$4,285 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.