There have been a few economic studies which have attempted to identify and quantify the benefit of an airport to the regional economy.One of these studies was performed by C-E-I-R, Inc. in 1960 for The Port of New York Authority. C-E-I-R estimated that in 1959, 121,000 employees earned $683,000,000 in the New York-New Jersey Metropolitan Region because of air transportation. Projecting the relationships, which C-E-I-R established, to 1971, it is estimated that employment generated by air transportation last year amounted to 190,000 with earnings of about 2 billion dollars.A study carried out in 1972 for the Los Angeles International Airport indicated that in 1970 the airport's five county Southern California market area was stimulated economically by a $1.4 billion payroll accounted for by 101,688 direct and indirect airport jobs. A similar economic stimulus was exerted by the expenditures of air visitors which amounted to an estimated $1.6 billion. By 1980, the airport's impact on the Los Angeles region will expand significantly with the airport industry payroll growing to $2.4 billion and expenditures by air visitors growing to $2.6 billion.Another study done in 1970 on the Dallas/Fort Worth Regional Airport indicated that by 1975 total employment stemming from air transportation would amount to 47,000 with regional purchases at $637 million. The study pointed out that the net economic impact in 1975 of the new airport (subtracting the capability of Love field, due to be closed) could be assessed at 15,000 employees and 202 million dollars.Such studies have not, for the most part, attempted to evaluate the economic dependency of industry on air transportation. The benefits of air transportation cannot be adequately assessed simply by the multiplier effect or input-output analysis.Environmental studies such as those done by the Commission on the Third London Airport and by the National Academy of Sciences on the extension of Kennedy Airport into Jamaica Bay have been most comprehensive in their analysis of environmental costs.The decision to build a new airport or expand an existing one is an increasingly difficult one, involving a complex mixture of institutional, environmental and economic issues. This makes it all the more imperative for the evaluators of these major public projects to give full weight to all the identifiable benefits and costs so that planning decisions can be made rationally with full knowledge of the consequences.