A spokesman for Frankfurt customs confirmed a report in Tuesday’s edition of daily Bild that the 30-year-old co-pilot was nabbed when the illegal weapons were found in his bag after a flight from Los Angeles.
He was also carrying 286 steel ball bearings, which are used as ammunition.
A criminal investigation had been launched, the spokesman said.
A Lufthansa spokeswoman said the airline was helping the investigators with their inquiries. She refused to comment on possible consequences for the pilot and stressed the man was being investigated rather than the airline.
Customs officers found the slingshots during a random bag search. A close-range, the high-powered devices could cause fatal injuries, the spokesman said.
The United States has liberal laws on such weapons. Nevertheless, slingshots were rarely found on passengers returning from the US because bags were usually strictly screened before a person boarded a plane in a city like Los Angeles.
It was particularly rare for airline staff to breach such clear provisions, he said. It was normal for customs to randomly search the bags of crew members, he added.
The case was handed over to the state prosecutors’ office. The pilot was potentially in breach of both weapons laws and air safety laws.