The National Transportation Safety Board (NTSB) has stated that a Port Authority firefighter driving a rescue truck heard repeated calls to "stop" before the March 22 crash at LaGuardia Airport that killed two pilots. The NTSB's preliminary report also stated that several other vehicles were gathered near taxiways at the time and the airport's systems could not spot that the landing plane might be on a collision course. The incident occurred shortly after the plane had just landed and was moving fast about 400 feet from a taxiway. The investigation also looked into air traffic control, procedures, and training, airplane components, and rescue operations.