Since 1978, the Essential Air Service (EAS) program has subsidized air service to eligible communities that would otherwise not have scheduled service. The cost of this program has risen as the number of communities being served and subsidies to air carriers have increased. At the same time, the number of carriers providing EAS service has declined. Given continuing concerns over the EAS program's long-term prospects, this report reviews: (1) the characteristics and current status of the EAS program; (2) factors affecting the program's ability to provide air service; (3) options for revising the program; and (4) tools for assessing the program, the options for its revision, and the program's performance. Charts and tables.