sentences:  There were no known attempts by ATC to warn Flight 1907 of the conflicting traffic.On 2 May 2007, the NTSB issued a Safety Recommendation document that included an interim summary of the investigation to date, as well as some immediate safety recommendations that the NTSB believes should be implemented by the U.S. Federal Aviation Administration (FAA) to enhance flight safety.The NTSB reported that the Embraer apparently experienced a Traffic Collision Avoidance System (TCAS) outage, unknown to its flight crew prior to the collision, according to the Cockpit Voice Recorder (CVR)