New Jersey ? Five airline passengers speaking in foreign languages and carrying “aircraft flight materials” were briefly detained Saturday until authorities determined they were simply returning to their home countries after attending a U.S. helicopter training school.

Passengers on American Airlines Flight 1874 became suspicious of the men, said Steven Siegel, a spokesman for the FBI’s Newark office.

A federal marshal on the plane notified authorities at Newark Liberty International Airport about the men’s behavior.

The men – identified only as four Angolan military personnel and an Israeli – had attended helicopter training school in Texas, Siegel said. Police officers took the men into custody soon after the plane landed, said a Port Authority spokesman.

After being questioned, the men were released about 6 p.m., Siegel said.