An electronic system is disclosed that uses air for cooling first and second orthogonally oriented arrays of parallel circuit boards. Air is drawn into the front of the system, passes alongside the circuit boards in the first array, takes a 90-degree turn, continues over the circuit boards in the second array, and takes another 90-degree turn to exhaust through the rear of the system. The circuit boards in the first array are cooled through a separate airflow path, which preferably also runs front-to-rear.