major update April 4
(props to Baz, see comments)
last edits 22 September
The Bomb Man Who Got Away
It's time to consider an amazing allegation I'd glossed over before as too complex. "Abu Elias" was a central and elusive figure in the PFLP-GC cell in Neuss tasked with downing an American airliner. The Neuss bomb-maker, Jordanian double-agent Marwan Khreesat, mentioned "Elias" in interviews with the FBI as essentially the fly in the ointment. Khreesat was supposed to keep live bombs out of terrorist hands, but this PFLP-GC higher-up was sent to inspect his work and then take possession of it and sneak it onto a plane (this is explained in detail elsewhere). One live bomb and "Abu Elias," at least, evaded the German police net just six weeks before the PA103 bombing.
For a while, he was a very wanted man. But then the Libyan villains were indicated instead, and by now, reportedly, "Abu Elias" is living safely in Washington DC with a government job and a desire to keep quiet. Below is a partial compendium of claims I haven't yet (or can't) rigorously verify. Much of this could be wrong but the picture that emerges is too amazing to miss seeing in its entirety.
No big surprise, "Abu Elias” was an alias, and and the first alleged true name attached to it was Khaisar Haddad. Most Internet postings of this simply repeat the conclusion of the Aangirfan blog (“Reportedly, Khaisar Haddad, known as Abu Elias, was an agent of the US government…”)  Otherwise the sources giving this name are old and of the questionable early 1990s revisionism of Juval Aviv, Lester Coleman, et al.
But these cite a clear external source, a report from Yassar Arafat’s PLO shortly after the indictments of Megrahi and Fhimah. An early mention was Time magazine’s controversial “Why Did They Die?” cover story, in April 1992. “Last month the Palestine Liberation Organization reported that [the bomb] was built by Khaisar Haddad (a.k.a. Abu Elias).”  By this telling, our subject built the bomb that wound up back in his hands, perhaps after being modified by Khreesat, who apparently made the other four himself (as linked above, see this post). Coleman and Goddard discussed this report in Trail of the Octopus:
In an 80-page report leaked to the press on both sides of the Atlantic, the PLO described a number of meetings between Ali Akbar Mohtashemi, the Iranian minister of the interior, Ahmed Jibril of the PFLP-GC and other officials in the late summer of 1988 to plan a revenge attack on an American airliner. According to the PLO's sources, the Toshiba radio-cassette bomb used to destroy Flight 103 had been built by Khaisar Haddad, also known as Abu Elias, a blond, blue-eyed Lebanese Christian member of the PFLP-GC, who passed the completed device on to an Iranian contact in Beirut. One must wonder if his fair appearance was part of his tool kit for getting past European security. But here Haddad just handed it off in Lebanon, counter to what Khreesat's story suggested. By the book's implausible narrative, the bomb was then slipped into Lebanese-American Khalid Jaafar's luggage using the CIA-protected heroin smuggling system at Frankfurt Airport.
Version Two: Goben to Megrahi
The identity of "Abu Elias" again surfaced at the Zeist trial in 2000 with vague news of the supposed deathbed confessions of PFLP-GC member Mobdi Goben ("Goben Memorandum") This reportedly explains how the enigma sneaked the bomb (directly it seems) into Khalid Jaafar's luggage, using just the system alleged in Trail of the Octopus. Beyond what the PLO's report said, Goben adds that "Elias" was a close relative of PFLP-GC founder Ahmed Jibril.  The defense wanted to explore it further, but Lord Advocate Colin Boyd, who was able to read the memo, blocked this as a "fishing expedition." 
The alleged true bomber formed part of Megrahi's 2002 appeal and the second appeal granted in 2007. The second time triggered a report from UK Sunday Express, announcing "Finger of Blame for Lockerbie Pointed at American Citizen." This "Abu Elias" sounds like the Goben version, described as a nephew of Jibril but as of summer 2007 anyway living in America and enjoying "a new identity the Sunday Express cannot divulge." 
The charge was repeated again by Megrahi and his legal team on the convict's compassionate release in August 2009. Again it was heralded by a story in the Express headlined "I'll Reveal True Identity of Bomber."
"The man Megrahi believes was Abu Elias now lives in a suburban neighbourhood near Washington’s Dulles airport, just a few miles from the White House and the Lockerbie memorial at Arlington National Cemetery. He even has his own Facebook social network page. ... He is the nephew of Syrian terror warlord Ahmed Jibril ... works as a schools engineer for the US government ..." The paper's team followed the name given (and hopefully more precise clues) and found him at home in suburban Washington. The man denied any involvement and asked to remain unnamed due to "the sensitivity of this matter," as he put it. But the paper reported "he has connections to at least two international terrorists,” one of which, interestingly, is Mohammed Abu Talb. Both Abus had lived in Sweden and had PFLP-GC links, and Abu Talb was the owner of some Maltese clothes similar to those inside the bomb suitcase, and onetime lead suspect for the Lockerbie bombing.
Besides these and his links to the PFLP-GC, the paper also said the Virginian had unspecified "links to the US intelligence services." He was known to the FBI and interviewed by them in August 1988, the report also says, and gives excerpts of a Megrahi appeal document that states: “The FBI had apparently investigated ‘X’ and knew he was the nephew of Ahmed Jibril ..." 
Poof, He's in Bush Land
Like the fictional Keyser Söze in The Usual Suspects it almost seems our Khaisar Haddad (?) walked right out of the 'police station' of suspicion as Keaton (Libya) burned for the crime. "And like that, poof. He's gone," down to the Olive Garden with the missus. On Megrahi’s release Member of Scottish Parliament Christine Grahame, who had met and campaigned for the prisoner, described the suspect as “living safely in Washington," possibly as an "intelligence asset." The man, whose new name she too knows, "must be deeply relieved that Megrahi was forced to drop his appeal and that he will never face justice for this atrocity.” 
However, according to the Express, Grahame was “believed to be considering naming the man in the Scottish Parliament chamber.” And two weeks later, she delivered, as this video from Channel 4 News and the official record of Scottish parliament for September 2 shows:
“Why have the US authorities not queried the true identity of Basel Bushnaq alias Abu Elias, a senior figure in the PFLP-GC at the time of the bombing and nephew of Ahmed Jibril, former head of that terrorist organisation? Basel Bushnaq currently resides in Washington DC and is in the employ of the schools division.” (See the video of her speech within this channel 4 production)
“Bushnaq” is an interesting choice of names, likely made while George W. Bush was president. It’s not the most anonymous choice. (see What's in a Name? for a closer look) More4 News in the UK contacted Mr Bushnaq about the allegations, and he replied, calling Grahame’s charges “reckless slander” and suggested "she stops this unless she has solid legal ground."  Speaking to the program, Ms Grahame explained “the name was presented in papers from the Scottish Criminal Case Review Commission, again as I said, evidence never seen in a Scottish court,” and will now apparently never be released. Having seen them herself, however, she was confident “the name I have given is a relevant name.” 
A different American Basel Bushnaq seems unlikely, as all listings of this unusual name I see give similar details – Basel or Basel A Bushnaq, of Washington DC, Herndon VA, and Franklin TN, age 53 or 54.  That’s the kind of variability one should expect within a slapdash record of one person rather than two getting mixed up. There is much left unknown here on how “Abu Elias” really translates to Khaisar Haddad and/or Basel Bushnaq, and Abu Elias' own true role in the bombing remains uncertain. I don’t want to be suckered into a false lead, but presuming he ever existed, Abu Elias got to somewhere, and D.C. makes a certain kind of sense. This could all be a mammoth mix-up as the suspect has said, either by goof or design of the “disinfo/distraction” type. Or it could be a genuine, festering clue of US acquisition and re-branding of the Lockerbie plot. It deserves being sorted out.
If this confusion is easily explained, Mr. Bushnaq, feel free to pop in and help us out – I’d be honored to host the death of a false lead and clear up the suspicion hovering over you if that’s easily enough done. If it is somehow more complex and sensitive than all that, I’ll take that as a sign of something but hold judgment about just what.
 Anonymous. "Reportedly, Khaisar Haddad, known as Abu Elias, was an agent of the US government and carried out the Lockerbie Bombing." Aangirfan. August 23 2009. http://aangirfan.blogspot.com/2009/08/reportedly-khaisar-haddad-known-as-abu.html
 "Why Did They Dies?" Time. April __ 1992. http://www.time.com/time/magazine/article/0,9171,159523,00.html
 Trail of the Octopus. Online Posting, Chapter 13
De Braeckeleer, Ludwig. "Dialog of a Vengeance Foretold part 107: The Goben Memorandum." Canada Free Press. October 17 2008. http://www.canadafreepress.com/index.php/article/5902
[5,6] Lambie, Derek. “Finger of Blame for Lockerbie Pointed at American Citizen.” Sunday Express. July 8 2007. http://janus.netro42.net/posts/view/12732
[7,8, 9] Borland, Ben. "I'll Reveal True Identity of Bomber." Sunday Express. August 23,2009 http://www.express.co.uk/posts/view/122299/-I-ll-reveal-true-identity-of-bomber%20UK%20NEWS
 Grahame, Christine (South of Scotland) (SNP). Remarks in Scottish Parliament, Official Report 2 September 2009. Col 19053 http://www.scottish.parliament.uk/business/officialreports/meetingsparliament/or-09/sor0902-02.htm
[11, 12] More 4 News. “Was Megrahi really the Lockerbie bomber?” 2 September 2009. http://www.channel4.com/news/article.jsp?id=3329697&time=181158