Flight 126 left the gate at John F. Kennedy International Airport Thursday night, only to return about an hour later after a passenger found strange wiring in the bathroom.
All 206 passengers were taken off the plane as a bomb squad did a search.
The wiring turned out to be non-explosive, but it certainly didn't belong there either.
The flight took off again for Madrid Friday morning. A Delta spokesperson said the flight had turned around and came back to JFK out of an abundance of caution.
The Associated Press contributed to this report.