American Airlines have put many USA to Europe routes on sale.
For example, fly from New York to Barcelona, Spain for only $408 roundtrip with American Airlines (see image below).
New York/Detroit/Atlanta/Minneapolis/Boston/Los Angeles/Miami/Seattle/Portland/Salt Lake City/Denver, USA
(same as DEPART)
Availability from September 2018 to February 2019 (excluding Christmas/New Year)
Complete the search box with the example dates listed above: