Here are some prices for flights around the time you requested. I don't know how long you plan to stay for, though.

Taxes are included.

BOS to MAD (May 28-Jun 6) $677
BOS to MAD (May 21-May 30) $706.82
BOS to MAD (May 14-May 23) $670.60

I am also currently looking into a new travel service, If anyone has any information on this service, please let me know. The fares seem alot cheaper, but I'm not sure if there is a catch or not.

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