Several airlines have lowered ticket prices from Boston to Spain to $400 and less for Barcelona and Madrid. KLM/SkyTeam have low $400s for airports across Spain. There are deals with all three alliances. Ticket prices are as low as $343 for Boston to Madrid flying Air Canada on a ticket from an online travel agency found through meta-search sites like Momondo.com and Skyscanner.com.
Low ticket prices are primarily for departures from Jan 9 – May 10, 2017.
United Airlines Boston BOS – Newark EWR – Madrid MAD – Newark EWR – Boston BOS
Skyscanner.com search Boston – Madrid
Air Canada $343 round trip Wed March 8 – Thu March 16
TravelMerry.com Air Canada ticket Boston BOS – Toronto YYZ – Madrid MAD – Toronto YYZ – Boston
$342.86 round trip Wed March 8 – Thu March 16
KLM Boston BOS – Amsterdam AMS – Valencia VLC – Amsterdam – Boston
American Airlines Boston BOS – New York JFK – Barcelona BCN – JFK – BOS