by radio. Ambulances could not talk with police units directly by radio. Commission member Lee Hamilton, in several television appearances related to a 2006 book on the topic of the WTC incident, reiterated this factually correct view. Aviation assets An example that was cited by Hamilton: during the incident the Police Department helicopter was unable to communicate with Fire Department units in order to warn them of the towers' imminent collapse. The NIST document suggests the helicopter may have been able to offer several minutes warning. "Several minutes" may have been enough to get some people from the lower floors outside. This warning of imminent collapse went out over at least one police radio channel but there is nothing showing it was relayed to other people or channels. FDNY operates at least two communications vans: one of which was brought to the scene at the WTC incident. The Commission report reveals the primary FDNY van was equipped to talk to NYPD helicopters but the backup van (which had no NYPD helicopter capability) was in use on September 11, 2001. In practice, many US helicopters used in emergency services are equipped with radios that allow communications on nearly any conventional two-way radio system, so long as the aircrew know the frequency and associated signaling tones. The radios usually have presets, like a car's broadcast radio, that allow some channels to be configured ahead of need. There was no information in the Commission report suggesting NYPD helicopters had such a capability. Cross-department While it is technically possible to implement communications across departments, doing so introduces a host of new training and incident command problems. These are problems that would need to be managed in addition to the existing set of issues present at any large incident. The ability to maintain command, and monitor the safety of, groups working at an incident is diminished if a group of firefighters cannot be reached because they've switched over to the EMS channel. This could cause people to be sent to rescue them when there was no need. Similarly, if the Manhattan EMS dispatcher can't reach an ambulance because they are on one of the fire channels, patient care is affected. New York City Police Commissioner Raymond Kelly, appearing on the Charlie Rose show, expressed his view that the existing radio systems performed satisfactorily during the WTC incident. In his view, the interoperability desired by the