The first officer, who Delta has declined to identify, was one of three pilots scheduled to make the Monday morning flight from Frankfurt to Atlanta.
The pilot was given a blood-alcohol test and faces possible charges of dangerous interference in air transport, according to news reports.
The pilot ''has been removed from active service during the investigation,'' Delta spokesman John Kennedy said.
Delta said the flight, which had 156 passengers on board, was delayed about two hours. Such international flights normally require a third pilot as a reserve. But the Boeing 767 took off with one captain and one first officer by changing its destination to Boston to keep the flight time below the Federal Aviation Administration's eight-hour cap. The flight continued to Atlanta after changing crews.
