Man With No Ticket or Passport Flew From Copenhagen to Los Angeles, F.B.I. Says

How hard is it to jump on an international flight to the United States with no ticket and no passport?

One man managed to do it last month after he passed through security at Copenhagen Airport in Denmark and flew on a Scandinavian Airlines flight to Los Angeles International Airport, carrying only Russian and Israeli identification cards in his bag, prosecutors said.

The man, Sergey Vladimirovich Ochigava, spoke to federal law enforcement officers, with the help of a Russian-speaking federal agent, on Nov. 5, the day after his flight landed and he was detained in Los Angeles. But the interview seemed only to deepen the mystery surrounding his travel.

He told the agents that he had a Ph.D. in economics and marketing and had worked as an economist in Russia a long time ago, according to an F.B.I. affidavit. He said he had not slept in three days and “did not understand what was going on,” the affidavit says.

He said he “might have had” a plane ticket to the United States, but was not sure, according to the affidavit. Mr. Ochigava also said he “did not remember how he got on the plane” and “would not explain how or when he got to Copenhagen, or what he was doing there,” the affidavit says. He also “claimed he did not remember how he went through security without a ticket,” it says.

Mr. Ochigava was indicted by a federal grand jury last month on a charge of being a stowaway on an aircraft, a felony that carries a maximum sentence of five years in prison. He has pleaded not guilty, and his trial is scheduled to begin on Dec. 26. His federal public defender, Erica Choi, did not immediately respond to a request for comment on Tuesday.

Thom Mrozek, a spokesman for the U.S. Attorney’s Office for the Central District of California, said the authorities believed that Mr. Ochigava was a Russian citizen and had not confirmed any legal status he might have in Israel. The documents in his possession indicate that he is 46 years old, Mr. Mrozek said.

Lise Agerley Kürstein, a Copenhagen Airport representative, said that Mr. Ochigava was seen on airport surveillance images “without a valid ticket.”

“Copenhagen Airport has provided photo and video material to the authorities who are investigating the case,” she said. “We take the matter very seriously, and it will be included in the work we continuously do to adjust and tighten our guidelines to improve security.”

Scandinavian Airlines said in a statement on Tuesday that it could only confirm a “situation regarding a passenger” on a flight from Copenhagen to the United States, and that the matter was being investigated by the authorities in both countries.

According to the affidavit, crew members on Scandinavian Airlines Flight 931 did not see Mr. Ochigava’s boarding pass but noticed that he initially sat in seat 36D, which was supposed to be unoccupied, and then wandered around the plane and kept changing his seat during the 12-hour flight.

Mr. Ochigava asked for two meals during each meal service, and “at one point attempted to eat the chocolate that belonged to members of the cabin crew,” the affidavit says. One crew member said Mr. Ochigava tried to talk to other passengers, “but most of the passengers ignored him,” according to the affidavit.

After the plane landed in Los Angeles at 1 p.m., Mr. Ochigava approached a Customs and Border Protection checkpoint and, speaking in English, told an officer that he had left his passport on the plane. But the airline did not find any passport there, the affidavit says.

Officers searched Mr. Ochigava’s bag and found a Russian identification card, used for travel within Russia, but not an international passport required for entry into the United States, according to the affidavit.

Mr. Ochigava also had an Israeli identification card, but there was no record that he had applied for the electronic travel authorization that Israelis need to enter the United States, the affidavit says.

An officer searched the State Department’s visa database but could not find any record that Mr. Ochigava had applied for or had received a visa, the affidavit says.

Another search of all the passengers on the Scandinavian Airlines flight, along with all the passengers who had arrived at Los Angeles International Airport on every European flight before 3 p.m. that day, confirmed that they were all accounted for, the affidavit says.

A day later, Mr. Ochigava allowed federal agents to look at six photos on his phone before he turned it off, according to the affidavit. But those, too, seemed to shed little light on his travel.

The most recent photo showed television screens displaying information for flights flying all over the world, including to Amsterdam, Munich and London, the affidavit says. The other photos, according to the affidavit, showed screengrabs from a maps app of a hostel in Kiel, Germany, and street maps of “an unknown foreign city.”