Aviation congestion and delay is an issue of long standing. Statistically, there was a significant increase in congestion and delay throughout the national aviation system in 2007. The situation has been especially noticeable at certain key airports, namely the New York region in general and John F. Kennedy International Airport (JFK) in particular. The Department of Transportation (DOT) and its operating agency, the Federal Aviation Administration (FAA), have promised to take actions aimed at reducing congestion and delay both in the short and long terms. In the short term, DOT is proposing to address the JFK situation through administrative and economic measures that would likely restrict or otherwise provide for the allocation of flights into the airport during specific periods of time. More detail on DOT's plans is expected to be available in the latter half of December 2007. In addition to the proposals likely to be made by DOT, there are other potential near-term fixes that can be considered to add system-wide capacity to the aviation system. These include, but are not limited to: airspace redesign, use of military airspace, and airspace flow control. Over the longer term the FAA is primarily relying on modernization of the air traffic control system through the Next Generation Air Transportation System (NGATS or NextGen) and the creation of new airport infrastructure to provide major reductions in aviation congestion and delay. This report discusses the causes of congestion and delay in the current context. It also discusses some technological and administrative mechanisms that might be employed to mitigate these problems. This discussion is followed by an overview of demand management (economic) remedies to congestion as they might be applied in an airport/airspace environment, and discusses the rather limited historical experience with the use of these mechanisms. Finally, the report concludes with a legal overview of how specific congestion remedies, in particular those involving aviation system pricing, might be applied and administered. Over the past four years, system-wide airline passenger volumes have continued to grow, now surpassing pre-9/11 levels. Along with this growth, flight delays and cancellations have also increased, and statistics indicate that the percentage of flights delayed 15 minutes or more in 2007 may surpass the prior record set in 2000. The percentage of cancelled flights is also up, although not quite as high as the percentage of cancellations experienced in 1999, 2000, and 2001 (see Figure 1 ). Some also point out that delay statistics alone do not tell the whole story. This is because airlines have, in many cases, opted to lengthen scheduled flight times, particularly along heavily congested and frequently delayed routes. A comparison of present day airline schedules to 1997 schedules found that published trip times are about 10% higher than they were 10 years ago. Additional schedule adjustments could be forthcoming and may further increase typical travel times, particularly in response to recent Administration announcements that it would consider operation of chronically delayed flights to constitute an "unfair and deceptive practice." Despite airline schedule adjustments that have increased planned-for trip times, airline delays are still ticking upward. As a consequence of this increase in delays, combined with airline schedule padding and passengers factoring additional wait times at security screening checkpoints into their travel plans, airline passenger trips are getting longer on average and travelers often face more hassles. Consumer complaints and media coverage of air carrier service deficiencies and cases of extensively delayed flights have put the specific issue of air carrier flight delays in the spotlight during the summer of 2007. In response, the DOT has convened a task force consisting of senior management to assess persisting problems with airline delays and consumer service, and has convened a special aviation rulemaking committee (ARC), consisting of aviation stakeholders representing airlines, airports, general aviation users, and airline consumers, to specifically address delays and other airline service issues in the New York metropolitan area. Based on the findings and recommendations of these groups, which are expected before the end of calendar year 2007, the DOT intends to propose options to address and remedy airline delay and customer service problems. Congress has taken a particular interest in this issue as these growing concerns over airline service have paralleled ongoing legislative action to reauthorize the activities of the FAA and the revenue mechanisms for funding the operations of the national airspace system. While there are broad concerns over aviation congestion and delay at many of the nation's busy airports, there is particular concern regarding airline service and performance at major airports in the New York metropolitan area where delay problems are the most acute. On-time arrival and departure statistics for the past two years compiled by the DOT's, Bureau of Transportation Statistics (BTS) have consistently ranked the three New York metropolitan area commercial passenger airports—Newark Liberty (EWR), John F. Kennedy International (JFK), and LaGuardia (LGA)—at or near the bottom of the list among the busiest 32 airports in the United States. From January 2007 through August 2007, about one out of every three flights arrived or departed more than fifteen minutes late at these airports. Between January 2002 and September 2007 at these three airports, arrival and departure delays were typically around one hour in length. At Newark Liberty Airport, where delays have consistently been the worst among busy U.S. airports, departure delays averaged 67 minutes and arrivals delays averaged 73 minutes over the time frame from September 2006 through September 2007. According to the FAA, over the summer of 2007, 44% of all air delays experienced throughout the United States occurred in the New York, New Jersey, and Philadelphia region. What's more, there was a dramatic increase in the percentage of flights cancelled at all three of these airports in 2007 compared to prior years. From January through September 2007, JFK saw 3.18% of its flights cancelled, LGA had 4.81% of its flights cancelled, and at EWR, 3.65% of scheduled passenger flights were cancelled. Not only are these cancellation rates much higher than previous years, but they are also considerably higher than the system-wide averages presented in Figure 1 . While many travelers perceive that delays are frequently associated with weather, actual delays directly attributable to severe weather conditions account for only a relatively small portion of total system-wide delays (about 6% of all air carrier delays from June 2003 through August 2007). Rather, delays are most readily attributable to a combination of the current system's inability to cope with weather, congestion, and other factors affecting the efficient flow of traffic at major airports and along crowded airways. These types of delays, referred to as national aviation system delays, account for about 31% of all air carrier delays and are the types of delays that the DOT believes can be remedied through investment in new technologies and more efficient procedures for air traffic management. Other sources of delays include air carrier delays arising from maintenance difficulties and inefficiencies in air carrier operations which account for about one quarter (27%, to be exact) of all delays. Also, the cascading effects resulting from aircraft arriving late that cannot be turned around in time to maintain outbound flight schedules account for 36% of all flight delays. However, the root causes of initial schedule delays that produce these cascading delays throughout an operational day can be primarily traced back to system inefficiencies and air carrier scheduling inefficiencies and constraints. Despite heightened aviation security, security related delays have had a negligible impact (less than 1% of flight delays) on air carrier operations (see Figure 2 ). Analysis of airline schedule delays and cancellations across the entire system, and more specifically at the three New York area airports, point to no one single cause, but rather a variety of potential contributing factors. These factors can be grouped into three broad categories: Airline Scheduling and Equipage Constraints on Airport and Air Traffic Control System Capacity; and Business Jets and Other High-Performance General Aviation Aircraft Operations The single leading cause of delays is the cascading effects of aircraft arriving late. Examining the trends in flight delay causes since June 2003 reveals that the largest increase among delay factors is also late aircraft arriving. This may, in part, be an indicator of possible airline over-scheduling and/or increased fleet utilization. In recent years, efforts to cut operational cost at airlines have driven airlines to reduce turn times (i.e., the time aircraft spend parked at the gate being serviced between flights). These data suggest that either the airlines themselves, the airport infrastructure, the FAA air traffic management system, or some combination of these aviation system components cannot fully accommodate this increased operational tempo. The result is cascading delays as an operational day progresses. This is also evidenced in statistics showing an increase in delays as it gets later in the operational day (see Figure 3 ). It seems somewhat paradoxical that the increased operations tempo can actually contribute to increased delays. To put this into perspective, it is useful to examine air carrier fleet trends. In 2000, mainline passenger airlines operated 4,488 jets compared to an estimated 3,886 in 2006. Over the same period, the number of aircraft operated by regional carriers, which are primarily smaller regional jets, grew from 2,274 in 2000 to an estimated 2,743 in 2006. Taking these two industry components together, the number of operating passenger aircraft declined from 6,762 in 2000 to an estimated 6,629 in 2006, roughly a 2% decrease. Looking solely at large jets, however, the trend is much more evident. Large jets in service have declined from 4,462 in 2000 to an estimated 3,827 in 2006, roughly a 14% decline. Whereas large jets made up about 66% of the total scheduled passenger service fleet in 2000, today large jets make up about 58%. In terms of the percentage of jet aircraft in airline operations, large jets made up about 88% of all jets used in scheduled passenger service in 2000, whereas in 2006, large jets comprised only 68% of all operating scheduled passenger jets. The trend over the past five years has clearly been toward reducing the number of large jets and increasing the number of smaller regional jets.