[What follows is an excerpt from the Wikipedia article on Dr Jim Swire:]
On 18 May 1990, Swire took a fake bomb on-board a British Airways flight from London's Heathrow airport to New York's JFK* and then on a flight from New York JFK to Boston to show that airline security had not improved; his fake bomb consisted of a radio cassette player and the confectionery marzipan, which was used as a substitute for Semtex. Some American family members asked Swire to keep the news of the stunt quiet; it became public six weeks later. Susan and Daniel Cohen, parents of Pan Am Flight 103 victim Theodora Cohen approved of the plan, while some other family members of American victims did not.**
* Fineman, Mark (6 July 1990). "TERRORISM / ONE MAN'S CRUSADE : Fake Bomb Shows Hole in Security : The father of one of the victims of the Pan Am 103 tragedy demonstrates that it could happen again". Los Angeles Times.
**Cohen, Susan and Daniel. "Chapter 16." Pan Am 103: The Bombing, the Betrayals, and a Bereaved Family's Search for Justice. New American Library. 2000. 225.