Then both a cargo and passenger plane would be flying blind. There is the possibility that if a cargo and a passenger jet were on a collision course, the cargo jet would maneuver in the same direction that TCAS is telling the passenger pilot to move. This could not happen if both planes had TCAS because the system communicates between the two planes computers and instructs one plane to climb and the other to descend. This was done in the belief that TCAS systems aboard other passenger aircraft would initiate an escape maneuver. The chances of a collision are greater today because of the rapid growth of the air cargo industry.
Many cargo planes travel at night, when visibility is low.
The greatest danger of a mid-air collision exists near airports where planes are flying in close quarters. The level of risk is heightened by the fact that these cargo aircraft fly without TCAS and normally land and take off at night at busy airports which serve as hubs for the cargo industry. The cargo industry does not consider a collision between two cargo planes to involve a significant loss of life, but the greatest danger of a collision is near airports, which normally are located in the vicinity of metropolitan areas. A collision between two cargo planes over a city could result in a tragic scenario.