The American plane, a 22 year old Boeing 777-200 (registration N754AN) crossed in front of the Delta jet that was in its takeoff roll. Air traffic control saw this happening and at almost the last possible moment called out to Delta to abort takeoff, out of fear the two planes would collide (“Shit! Delta 1943 cancel takeoff clearance!”).
We know a little bit more than was immediately available when this incident was first disclosed.