[On this date in 1988 the German police arrested seventeen men at Neuss in operation “Autumn Leaves” (Herbstlaub). What follows is excerpted (with citations removed) from the relevant article in Wikipedia:]
For many months after the bombing, the prime suspects were the Popular Front for the Liberation of Palestine—General Command (PFLP-GC), a Damascus-based rejectionist group led by former Syrian army captain Ahmed Jibril, sponsored by Iran. In a February 1986 press conference, Jibril warned: "There will be no safety for any traveler on an Israeli or U.S. airliner" (Cox and Foster 1991, p28).
Secret intercepts were reported by author, David Yallop, to have recorded the Iranian Revolutionary Guards (Pasdaran) in Baalbeck, Lebanon, making contact with the PFLP-GC immediately after the downing of the Iran Air Airbus. Israeli intelligence (Mossad) allegedly intercepted a telephone call made two days after PA 103 by Mohtashemi-Pur, Interior Minister in Tehran, to the chargé d'affaires at the Iranian embassy in Beirut, instructing the embassy to hand over the funds to Jibril and congratulating them on the success of "Operation Intekam" ('equal and just revenge'). (...)
Jibril's right-hand man, Hafez Dalkamoni, set up a PFLP-GC cell which was active in the Frankfurt and Neuss areas of West Germany in October 1988, two months before PA 103. During what Germany's internal security service, the Bundesamt für Verfassungsschutz (BfV), called Operation Herbstlaub ('Operation Autumn Leaves'), the BfV kept cell members under strict surveillance. The plotters prepared a number of improvised explosive devices (IEDs) hidden inside household electronic equipment. They discussed a planned operation in coded calls to Cyprus and Damascus: oranges and apples stood for 'detonating devices'; medicine and pasta for 'Semtex explosive'; and auntie for 'the bomb carrier'. One operative had been recorded as saying: "auntie should get off, but should leave the suitcase on the bus" (Duffy and Emerson 1990). The PFLP-GC cell had an experienced bomb-maker, Jordanian Marwan Khreesat, to assist them. Khreesat made at least one IED inside a single-speaker Toshiba Bombeat 453 radio cassette recorder, similar to the twin-speaker model RT-SF 16 Bombeat that was used to blow up PA 103. However, unlike the Lockerbie bomb with its sophisticated timer, Khreesat's IEDs contained a barometric pressure device that triggers a simple timer with a range of up to 45 minutes before detonation.
Unbeknown to the PFLP-GC cell, its bomb-maker Khreesat was a Jordanian intelligence service (GID) agent and reported on the cell's activities to the GID, who relayed the information to Western intelligence and to the BfV. The Jordanians encouraged Khreesat to make the bombs but instructed him to ensure they were ineffective and would not explode. (A German police technician would however be killed, in April 1989, when trying to disarm one of Khreesat's IEDs). Through Khreesat and the GID, the Germans learned that the cell was surveying a number of targets, including Iberia Flight 888 from Madrid to Tel Aviv via Barcelona, chosen because the bomb-courier could disembark without baggage at Barcelona, leaving the barometric trigger to activate the IED on the next leg of the journey. The date chosen, Khreesat reportedly told his handlers, was October 30, 1988. He also told them that two members of the cell had been to Frankfurt airport to pick up Pan Am timetables.
Acting upon this intelligence, the German secret police moved in to arrest the PFLP-GC cell on October 26, raiding 14 apartments and arresting 17 men, fearing that to keep them under surveillance much longer was to risk losing control of the situation. Two cell members are known to have escaped arrest, including Abu Elias, a resident of Sweden who, according to Prime Time Live (ABC News November 1989), was an expert in bombs sent to Germany to check on Khreesat's devices because of suspicions raised by Ahmed Jibril. Four IEDs were recovered, but Khreesat stated later that a fifth device had been taken away by Dalkamoni before the raid, and was never recovered. The link to PA 103 was further strengthened when Khreesat told investigators that, before joining the cell in Germany, he had bought five Toshiba Bombeat cassette radios from a smugglers' village in Syria close to the border with Lebanon, and made practice IEDs out of them in Jibril's training camp 20 km (12 mi) away. The bombs were inspected by Abu Elias, who declared them to be good work. What became of these devices is not known.
Some journalists such as Private Eye's Paul Foot and a PA 103 relative, Dr Jim Swire, believed that it was too stark a coincidence for a Toshiba cassette radio IED to have downed PA 103 just eight weeks after the arrest of the PFLP-GC cell in Frankfurt. Indeed, Scottish police actually wrote up an arrest warrant for Marwan Khreesat in the spring of 1989, but were persuaded by the FBI not to issue it because of his value as an intelligence source. In the following spring, King Hussein of Jordan arranged for Khreesat to be interviewed by FBI agent, Edward Marshman, and the former head of the FBI's forensic lab, Thomas Thurman, to whom he described in detail the bombs he had built. In the 1994 documentary film Maltese Double Cross, the author David Yallop speculated that Libyan agents and agents paid by Iran may have worked on the bombing together; or, that one group handed the job over to a second group upon the arrest of the PFLP-GC cell members. The former CIA head of counter-terrorism, Vincent Cannistraro, who previously worked on the PA 103 investigation, was interviewed in the film and said he believed the PFLP-GC planned the attack at the behest of the Iranian government, then sub-contracted it to Libyan intelligence after October 1988, because the arrests in Germany meant the PFLP-GC was unable to complete the operation. Other supporters of this theory believed that whoever paid for the bombing arranged two parallel operations intended to ensure that at least one would succeed; or, that Jibril's cell in Germany was a red herring designed to attract the attention of the intelligence services, while the real bombers worked quietly elsewhere.
For many months after the bombing, the prime suspects were the Popular Front for the Liberation of Palestine—General Command (PFLP-GC), a Damascus-based rejectionist group led by former Syrian army captain Ahmed Jibril, sponsored by Iran. In a February 1986 press conference, Jibril warned: "There will be no safety for any traveler on an Israeli or U.S. airliner" (Cox and Foster 1991, p28).
Secret intercepts were reported by author, David Yallop, to have recorded the Iranian Revolutionary Guards (Pasdaran) in Baalbeck, Lebanon, making contact with the PFLP-GC immediately after the downing of the Iran Air Airbus. Israeli intelligence (Mossad) allegedly intercepted a telephone call made two days after PA 103 by Mohtashemi-Pur, Interior Minister in Tehran, to the chargé d'affaires at the Iranian embassy in Beirut, instructing the embassy to hand over the funds to Jibril and congratulating them on the success of "Operation Intekam" ('equal and just revenge'). (...)
Jibril's right-hand man, Hafez Dalkamoni, set up a PFLP-GC cell which was active in the Frankfurt and Neuss areas of West Germany in October 1988, two months before PA 103. During what Germany's internal security service, the Bundesamt für Verfassungsschutz (BfV), called Operation Herbstlaub ('Operation Autumn Leaves'), the BfV kept cell members under strict surveillance. The plotters prepared a number of improvised explosive devices (IEDs) hidden inside household electronic equipment. They discussed a planned operation in coded calls to Cyprus and Damascus: oranges and apples stood for 'detonating devices'; medicine and pasta for 'Semtex explosive'; and auntie for 'the bomb carrier'. One operative had been recorded as saying: "auntie should get off, but should leave the suitcase on the bus" (Duffy and Emerson 1990). The PFLP-GC cell had an experienced bomb-maker, Jordanian Marwan Khreesat, to assist them. Khreesat made at least one IED inside a single-speaker Toshiba Bombeat 453 radio cassette recorder, similar to the twin-speaker model RT-SF 16 Bombeat that was used to blow up PA 103. However, unlike the Lockerbie bomb with its sophisticated timer, Khreesat's IEDs contained a barometric pressure device that triggers a simple timer with a range of up to 45 minutes before detonation.
Unbeknown to the PFLP-GC cell, its bomb-maker Khreesat was a Jordanian intelligence service (GID) agent and reported on the cell's activities to the GID, who relayed the information to Western intelligence and to the BfV. The Jordanians encouraged Khreesat to make the bombs but instructed him to ensure they were ineffective and would not explode. (A German police technician would however be killed, in April 1989, when trying to disarm one of Khreesat's IEDs). Through Khreesat and the GID, the Germans learned that the cell was surveying a number of targets, including Iberia Flight 888 from Madrid to Tel Aviv via Barcelona, chosen because the bomb-courier could disembark without baggage at Barcelona, leaving the barometric trigger to activate the IED on the next leg of the journey. The date chosen, Khreesat reportedly told his handlers, was October 30, 1988. He also told them that two members of the cell had been to Frankfurt airport to pick up Pan Am timetables.
Acting upon this intelligence, the German secret police moved in to arrest the PFLP-GC cell on October 26, raiding 14 apartments and arresting 17 men, fearing that to keep them under surveillance much longer was to risk losing control of the situation. Two cell members are known to have escaped arrest, including Abu Elias, a resident of Sweden who, according to Prime Time Live (ABC News November 1989), was an expert in bombs sent to Germany to check on Khreesat's devices because of suspicions raised by Ahmed Jibril. Four IEDs were recovered, but Khreesat stated later that a fifth device had been taken away by Dalkamoni before the raid, and was never recovered. The link to PA 103 was further strengthened when Khreesat told investigators that, before joining the cell in Germany, he had bought five Toshiba Bombeat cassette radios from a smugglers' village in Syria close to the border with Lebanon, and made practice IEDs out of them in Jibril's training camp 20 km (12 mi) away. The bombs were inspected by Abu Elias, who declared them to be good work. What became of these devices is not known.
Some journalists such as Private Eye's Paul Foot and a PA 103 relative, Dr Jim Swire, believed that it was too stark a coincidence for a Toshiba cassette radio IED to have downed PA 103 just eight weeks after the arrest of the PFLP-GC cell in Frankfurt. Indeed, Scottish police actually wrote up an arrest warrant for Marwan Khreesat in the spring of 1989, but were persuaded by the FBI not to issue it because of his value as an intelligence source. In the following spring, King Hussein of Jordan arranged for Khreesat to be interviewed by FBI agent, Edward Marshman, and the former head of the FBI's forensic lab, Thomas Thurman, to whom he described in detail the bombs he had built. In the 1994 documentary film Maltese Double Cross, the author David Yallop speculated that Libyan agents and agents paid by Iran may have worked on the bombing together; or, that one group handed the job over to a second group upon the arrest of the PFLP-GC cell members. The former CIA head of counter-terrorism, Vincent Cannistraro, who previously worked on the PA 103 investigation, was interviewed in the film and said he believed the PFLP-GC planned the attack at the behest of the Iranian government, then sub-contracted it to Libyan intelligence after October 1988, because the arrests in Germany meant the PFLP-GC was unable to complete the operation. Other supporters of this theory believed that whoever paid for the bombing arranged two parallel operations intended to ensure that at least one would succeed; or, that Jibril's cell in Germany was a red herring designed to attract the attention of the intelligence services, while the real bombers worked quietly elsewhere.