seems to realize the mistake. >> 601, stop your heading, stop the turn right there. stop your turn. stop your climb and stop your turn. >> the two planes came within nearly a mile of each other. the roughly 300 passengers on both flights may not have been aware of the close call but the pilots were left with questions as to what went wrong. >> 601, you know what happened there? >> basically crossinged directly over the top of each other. >> that's what it looked like. i had no idea what was going on in the tower. it was pretty narly looki looki >> reporter: this is the third incident in recent weeks where two planes got too close for comfort. all involving passenger planes. >> cnn's rene marsh reporting for us. there were 4,400 close calls in the air in 2012. if you do the math, that's more