Delta is offering very low fares from Austin, Texas, to European cities. They apply to travel in November and December only.
Cheap Flights: Austin to Madrid / Barcelona $559-$590 r/t – Delta + SkyTeam
Cheap Flights: Austin to London $659-$676 r/t – Delta + SkyTeam
Note that other airlines may match this fare, or even extend it earlier in the Fall 2016 and Spring 2017. Delta has been engaged in an airfare war with American, so American may well choose to do a match.