This was also reported on The News on Sept 12, 2002 edition. Here is the link:
Murtaza Bhutto proposed WTC attack in 1991: Carlos
CAIRO: Pakistani dissident Mir Murtaza Bhutto proposed the idea of using an airplane to hit targets in the United States as early as the spring of 1991, former terrorist Carlos the Jackal said in an interview published on Wednesday.
Carlos, whose real name is Ilich Ramirez Sanchez and who is currently serving a life sentence for murder in France, told the Arabic language daily Al-Hayat that Bhutto vetted the idea as a response to US strikes in Iraq, at a meeting of “anti-imperialist organisations” at an undisclosed location.
“The martyr Mir Murtaza Bhutto, secretary general of the Pakistani Zulfikar Organization, raised the idea of hitting the World Trade Centre in New York with an airplane,” Carlos said in a written response to questions submitted through his lawyer.
The groups had affirmed in a “spontaneous and unofficial way the need to respond with explosions in the United States” to the “terrible destruction in Iraq” inflicted during the 1991 Gulf War.
Carlos said that the security agency of a “progressive Arab state” had notified US authorities of the meeting, and that Sudanese security contacted the United States in 1993 with a list of possible terrorist targets that included the World Trade Centre and the Pentagon.
Both were hit on September 11 last year by airliners hijacked by members of Osama bin Laden’s al-Qaeda network, killing some 3,000 people. Carlos, once the world’s most wanted man, was arrested in 1994 in Sudan – where, he told Al-Hayat, he had travelled the year before to set up a revolutionary organization – and extradited to France. Three years later, he was sentenced to life in prison for the 1975 murder of three people in Paris.
Bhutto, estranged younger brother of former Pakistani prime minister Benazir Bhutto, formed the Al-Zulfikar Organisation to avenge the execution of their father, Zulfikar Ali Bhutto, after his overthrow in a military coup in 1977.
In 1981 the group staged the hijack of a Pakistani airliner in which one person was killed to secure the release of dozens of Bhutto followers from prison. Mir Murtaza Bhutto returned from a 16-year exile, spent mainly in Syria, in 1993, after his sister was elected prime minister for a second term, but immediately found himself in conflict with her. Released later, he was shot dead in a confrontation with police in Karachi in September 1996. Benazir, who denied involvement, was removed from office by President Farooq Leghari less than two months later.
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Whether its true or not depends on how much credibility Carlos the Jackal has, who is serving a life sentence and can claim to be the devil incarnate for all he cares.
I have also read it somewhere that Murtaza Bhutto’s organization had initially claimed responsibilty for the crash of C-130 plane that killed Zia.
Later, when it was disclosed that two Americans (including Ambassador to Pak) were also on the plane and perished as well, he and his organization retracted the claim 
