LaGuardia firefighter heard ‘stop’ before crash but didn’t know who it was for, report says

National Transportation Safety Board's preliminary report further says crash prevention system didn't generate alert

A firefighter whose truck collided with an Air Canada jet last month on a runway at New York's LaGuardia airport, killing both pilots, heard an air traffic controller warn stop, stop, stop" but didn't know who it was for, federal investigators said Thursday.

The National Transportation Safety Board said in a preliminary report on the 22 March collision that a crash prevention system for air traffic controllers didn't generate an audio or visual alert, and lights on the runway that act as a stop light for crossing traffic were on until about three seconds before the collision.