Osama bin Laden's son-in-law, Suleiman Abu Ghaith, has been found guilty of terrorism charges by a court in New York. Abu Ghaith (48) was spokesman for al-Qaeda in the wake of the 9/11 attacks.

The Kuwaiti testified he agreed to bin Laden's request to speak on videos to inspire new recruits for suicide missions.

"The storm of airplanes will not stop" Abu Ghaith warned in one October 2001 video played in court.

Another video, made the day after 9/11, shows him sat next to bin Laden and other al Qaeda leaders as they try to justify the attacks. As well as conspiracy to kill, Abu Ghaith was also convicted of providing support for terrorists.

He is the most senior al Qaeda figure to go on trial in America. He now faces life behind bars.

Abu Ghaith married bin Laden's eldest daughter - Fatima - five years ago.

US authorities had accused Ghaith of assisting Bin Laden, who was gunned down in a 2011 raid by American Navy SEAL commandos.

Ghaith "held a key position in al Qaeda, comparable to the consigliere in a mob family or propaganda minister in a totalitarian regime" said George Venizelos, the assistant director-in-charge of the FBI's New York field office.

"He used his position to persuade others to swear loyalty to Al-Qaeda's murderous cause. He used his position to threaten the United States and incite its enemies".

According to the indictment, he allegedly threatened Americans, warning them that a "great army is gathering" and "the storms shall not stop, especially the airplanes storm".

The indictment also stated Ghaith was "smuggled successfully from Afghanistan into Iran" in 2002.

Kuwait had stripped Ghaith of his citizenship a month after the 9/11 attacks, after he had appeared in widely circulated videos vowing more bloodshed against the United States and its allies.