Benchmarks are useful data that help frame discussions. However, they are not a substitute for the more detailed analysis that should precede major investment and policy decisions. In this sense they might be compared to a vital sign of human health, such as blood pressure. That simple indicator might be the starting point for a diagnosis, but more information would be wanted before recommending surgery. Similarly, capacity benchmarks help identify problem areas but are not, in themselves, an adequate basis for selecting remedies.

This issue is apparent in the case of Atlanta Hartsfield International Airport. The scheduled operations exceed the benchmarks several times daily in optimum weather and frequently under reduced rate conditions. The simple comparison of schedule to benchmarks suggests that some action is needed to curtail the schedule. However, air traffic controllers, airlines, and the airport operator have indicated in discussions that they are relatively comfortable with the current schedule and believe that it makes efficient use of the airport. Their judgment is based on vast experience and a broad understanding of air transportation. Some of the considerations are specific to Atlanta (favorable runway configuration, weather patterns, and airspace structure), some are applicable to transfer hub airports in general (the concentration of traffic into schedule peaks to allow passengers to make convenient transfer between flights, the ability to catch up with traffic between peaks in the schedule, and the ability of hubbing carriers to cancel and consolidate some flights during reduced rate conditions), and some are applicable to all busy airports (the premise that some amount of congestion and delay is not inconsistent with efficient and affordable air transportation).

• These benchmarks are estimates of a complex quantity that varies widely with weather conditions, runway configurations, and the mix of aircraft types. Capacity benchmarks assume there are no constraints in the en route system or the airport terminal area. They are useful for broad policy discussions and the development of long–term strategies.

• The optimum rate is defined as the maximum number of aircraft that can be routinely handled using visual approaches during periods of unlimited ceiling and visibility.
• The reduced rate is defined as the maximum number of aircraft that can be routinely handled during reduced visibility conditions when radar is required to provide separation between aircraft. This rate was determined for the most commonly used runway configuration in adverse weather conditions.

• The benchmarks reflect the number of takeoffs and landings per hour for the given conditions. These benchmarks can be exceeded occasionally and lower rates can be expected under adverse conditions.
• The FAA confirmed capacity benchmark rates in three ways:

• Benchmark rates for each airport were provided by the air traffic team at the facility and the airport operator and were based on their collective operational experience.
• Benchmark rates provided by the air traffic teams were compared to historical arrival and departure data (Aviation System Performance Metrics) to confirm that they represent the best performance of the airport.
• Using the FAA’s widely accepted airfield capacity computer model, benchmark rates were also calculated based on a set of standard performance characteristics.

• The resulting capacity benchmarks were then compared to carrier schedule data from the Official Airline Guide. Scheduled carrier operations constitute a significant part, but not all, of an airport’s traffic. Excluded are general aviation and military operations, non-scheduled flights and some cargo operations. These typically account for between 1 and 30% of the total traffic at the 31 airports studied.
• Human factors play a critical role in the benchmark rates reported by the air traffic facility. Benchmarks are strongly affected by how busy the airport is and how aggressively the management team sets target rates.
• Six airports were selected for on-site visits to validate the methodology: Atlanta, Chicago, Dallas-Fort Worth, St. Louis, Memphis, and Detroit. These on-site visits included discussions with local air traffic personnel, airport authorities, and air carriers serving the airport. For the other airports, discussions were conducted with managers at the local air traffic facility.
• The individual benchmark summaries compare projected growth in capacity with projected growth in demand to understand the relationship between future airline demand and airport capacity. Demand is based on the Terminal Area Forecast, the FAA’s projection of aviation activity at select U.S. airports, and is revised annually to reflect current and anticipated economic and social conditions.
• Historically, there are several measures of delay commonly used. (See appendix) The measure used herein to identify the most delayed airports is the percent of aircraft delayed more than 15 minutes from the FAA’s Operations Network (OPSNET).

• Automatic Dependent Surveillance-Broadcast/Cockpit Display of Traffic Information with Local Area Augmentation System (ADS-B/CDTI with LAAS) – provides a cockpit display of the location of other aircraft and will help the pilot maintain the desired separation more precisely.
• Flight Management System/Area Navigation (FMS/RNAV) Routes – allow a more consistent flow of aircraft to the runway.
• Passive Final Approach Spacing Tool (pFAST) – assists the controller with runway assignment and sequencing for aircraft and better flow of traffic into the terminal area.
• Simultaneous instrument approaches – allow full independent use of two or more runways for landings in adverse weather conditions.
• Precision Runway Monitor (PRM) – a high update radar system that allows simultaneous instrument approaches to parallel runways as close as 3000 feet apart. Also helps in procedural applications such as Simultaneous Offset Instrument Approaches (SOIA) where applicable.
• Land and Hold Short Operations (LAHSO) – allows independent arrivals for specific aircraft types on intersecting runways, where runway geometries permit.

• Benefits from planned improvements assume that all required infrastructure and regulatory approvals will be in place including aircraft equipment, airspace design, environmental reviews, radio frequencies, training, etc. as needed.
• In general, the benchmarks do not consider any limitation on airport traffic flow that may be caused by non-runway constraints at the airport or elsewhere in the National Airspace System. Such constraints may include:

• Taxiway and gate congestion, runway crossings, slot controls, construction activity;
• Terminal airspace, especially limited departure headings;
• Traffic flow restrictions caused by en route miles-in-trail restrictions, weather, or congestion problems at other airports; and

• Seasonal limitations due to high temperatures that restrict aircraft climb rates.

• The benchmark study predicts that, in 10 years, the first 6 of the 8 airports above plus Los Angeles will still have significant passenger delays. New runways at Atlanta and Boston should alleviate delays at those two airports.
• Table 1 shows the capacity benchmarks for the 31 airports studied.
• The capacity of airports decreases in adverse weather conditions, which may include poor visibility, unfavorable winds, or heavy precipitation. The reduced rate reflects the capacity benchmark for the most commonly used configuration in adverse weather. Under very low ceiling/visibility in Instrument Meteorological Conditions (IMC), capacity is even lower.
• Extent of capacity loss during operations at reduced rates (as compared to the optimum) varies widely across the 31 airports, e.g.,

• At Cincinnati and Minneapolis-St. Paul, it is minimal (2 percent)
• At some airports like Detroit, Washington Dulles, and Houston, it is relatively small (10 percent or less)
• At other airports like St. Louis and San Francisco it is very high (about 40 percent)

These differences are due to different runway configurations and operational procedures in adverse weather at each airport.

• Most airports are able to handle demand under good weather conditions (i.e., optimum capacity). New York LaGuardia is an exception and is the highest ranked airport for delay rates in the year 2000. Looking at the number of aircraft delayed significantly (i.e., greater than 15 minutes), LaGuardia had 156 delays per 1,000 aircraft operations and Newark was a distant second at 81 delays per 1,000 aircraft operations (Table 2).
• During good weather, delays are generally small and manageable.
• During bad weather, capacity is lower and results in even more delays. Overall, LaGuardia, Newark, Chicago O’Hare, and San Francisco have the highest delay rates (57 to 156 delays per 1,000 aircraft operations). Several airports such as Las Vegas, Baltimore-Washington, Denver, and Salt Lake City do not have any significant delay problems (less than 10 delays per 1,000 aircraft operations).
• New runways planned for 14 airports provide significant capacity increases but the amount of the increase varies from site to site.

• Detailed plans for new runways in the next 10 years were available for Atlanta, Houston, Dallas/Fort Worth, Phoenix, Washington Dulles, St. Louis, Detroit, Cincinnati, Minneapolis-St. Paul, Miami, Seattle-Tacoma, Orlando, Charlotte, and Denver. Additional airport operators are considering new runways, but their plans are not advanced to the point where the impact can be estimated.
• Nominal increases are in the range of 30 to 60 percent at Atlanta, Houston, Phoenix, Washington Dulles, Seattle-Tacoma, and Minneapolis-St. Paul.
• Some airports with high capacity configurations at their disposal today have a lower percentage of capacity increase from new runways (e.g., Denver).

• Technology improvements also provide capacity increases – most are in the 3 to 8 percent range.
• Procedural enhancements also hold promise. Depending on the airport, the enhancements could account for an additional 5 to 10 percent improvement in operations.
• For those airports operating close to capacity, technology and procedural changes could have a significant impact in improving capacity.
• Projected demand growth to 2010 at these 31 airports varies from 4 percent at Washington National Airport to 42 percent at Orlando.

* Estimates assume that new runways (where applicable) are in place

** Numbers include compounding effects of new runways and new technologies and are not strictly additive