Report prepared by C. Spicer, J. Hubbe, J. Anderson, K., Business, B. Cooke, R. Hannigan, T. Kelly, G. Laws, R. Lee, D. Sharp, P. Sticksel, C. Turner, and G. Ward. Reported to ENSR Consulting and Engineering/U.S. Environmental Protection Agency. Contract Number: 88041 "April 1991." "This report describes an aircraft sampling program carried out in the eastern United States in spring, 1990. The aircraft measurement program was part of the Acid Model Operational Diagnostic Evaluation Study (Acid MODES). This report is focussed [sic] on the measurements made aboard Battelle's Gulfstream (G-1) research aircraft as part of the spring, 1990 Acid MODES field experiment. This report describes the approach and methods used, it summarizes the data collected aboard the G-1 during the field program, and it describes the structure and format of the archived data"--Page 1. "Vol. 1 contains introductory materials, descriptions of flight patterns and experimental procedures, a discussion of quality assurance procedures and results, sample summaries, and a guide to the G-1 aircraft database. Vol. 2 contains plots and tables of the aircraft data in four appendices"--Cover letter. Includes bibliographical references.