The report separately identifies and analyzes the possible improvements needed to prevent or reduce aircraft delays at ten high density airports with pending congestion problems. The original report dated April 1969 provided analysis for eighteen of the Nation's highest density airports which were experiencing serious congestion. Discussion is presented on the causes contributing to aeronautical congestion and on the current operational status of each airport. The supplemental report is concerned primarily with physical construction projects which will enhance the particular airport's airfield capacity such as high-speed exit taxiways, parallel runways, and navigational aids. It also examines certain procedural improvements such as intersection takeoffs and part-time use of taxiways as VFR runways. Each airport improvement, where possible, has been evaluated from a cost vs. delay benefit savings viewpoint. The result is a series of recommended actions for each surveyed airport with emphasis given to those items which can be constructed or implemented and placed in operation within one to four years. (Author).