Federal authorities on Wednesday unsealed an indictment charging a Kenyan man with trying to stage a 9/11-style attack on the United States on behalf of the terrorist organization al-Shabab.

Cholo Abdi Abdullah, 30, who was arrested in the Philippines in 2019, was transferred to U.S. custody Tuesday on charges he conspired to hijack an aircraft and slam it into a building.

He pleaded not guilty to terrorism-related charges during a brief court appearance Wednesday and was ordered held without bond. He faces a mandatory minimum 20 years in prison if convicted. His defense attorney declined to comment.

Prosecutors said Abdullah got flight training in the Philippines between 2017 and 2019 and obtained a pilot�s license in preparation for an attack. During that time, authorities said in a news release, Abdullah researched �the means and methods to hijack a commercial airliner,� including how to breach a cockpit door and �information about the tallest building in a major U.S. city.�

�This case, which involved a plot to use an aircraft to kill innocent victims, reminds us of the deadly threat that radical Islamic terrorists continue to pose to our nation,� Assistant Attorney General for National Security John Demers said in a statement.

Acting Manhattan U.S. Attorney Audrey Strauss called it a �chilling callback to the horrific attacks of September 11, 2001.�

Abdullah, prosecutors said, started planning the attack in 2016 under the direction of an al-Shabab commander who was also involved in planning a deadly attack in 2019 on a hotel in Nairobi, Kenya.

The State Department in 2008 designated al-Shabab, which means �the youth� in Arabic, as a foreign terrorist organization. The militant group is an al-Qaida affiliate that has fought to establish an Islamic state in Somalia based on Shariah law.

Prosecutors, in announcing the hijacking plot, said the extremist group recently �embarked on a string of terrorist attacks� following the United States� decision to move its embassy in Israel to Jerusalem.

Those include the 2019 attack that killed some 21 people � including an American businessman who survived the 9/11 attack on the World Trade Center � at a Nairobi hotel.

(AP)