There are WAY too many combinations to sort out here, but almost every U.S. city is on sale in the $400s to Europe! More info and list of destinations can be found on The Flight Deal. But hurry on over to Google Flights and book your next trip!
Airline: American/One World Alliance
Dates: Jan - March 2018
Our booking tip: Using Google Flights, insert your home airport for "Departure" and enter "Europe" into "Arrival." Select a random week in February to see list of cities and lowest prices. Once you've picked your destination, select it for "arrival" and use flexible calendar search between Jan and March to find your exact dates. You can then book direct with airline, or plug dates and destination into Momondo to see if cheaper through an Online Travel Agency (OTA).
Comment below and let us know if you book!