Marion Britton was a 53-year-old assistant regional director of the US Census Bureau when she died on board United Airlines Flight 93.
Just before the plane crashed Britton called her friend Fred Fiumano. Most media accounts, and two brief FBI documents say these calls were made by cellphone. However, evidence presented at the Moussaoui trial stated she used an airfone, a contradiction seized upon by 9/11 researchers including David Ray Griffin. History Commons sum up the story here:
Does the universal initial reporting of the call as from a cellphone mean the FBI presented false evidence at the Moussaoui trial? Not necessarily. Here's a portion of an FBI interview from September 20, 2001:
Fiumano assumed Britton was using a borrowed cellphone based on the fact that he was given a strange number, then. Presumably he repeated this assumption without qualification originally, and the media then repeated the story. Or perhaps they omitted the qualification because they didn't consider it significant.
Fiumano may have assumed correctly, but it's also possible that Britton used an airfone and gave him an incoming phone number for that. Or Britton may have used an airfone, not realised it could receive incoming calls, and given Fiumano the cellphone number of her neighbour. Whatever the reality, the detailed Fiumano interview does not rule out the possibility that Britton called from an airfone, and therefore it cannot be said to contradict the FBI's phone call evidence from the Moussaoui trial.