Summary: GAO discussed Federal Aviation Administration (FAA) appropriations issues, specifically: (1) the work of the FAA systems engineering and integration contractor (SEIC); (2) how much air traffic control (ATC) modernization could cost; (3) when FAA would complete modernization; and (4) how many controller and maintenance technicians FAA would need. GAO found that: (1) although SEIC contributed to the National Airspace System (NAS) plan, its control over the system design was limited; (2) SEIC employees are currently in an improper employee-employer relationship with FAA; (3) FAA assigned SEIC the site-specific design work at air traffic control centers, but SEIC believed that the work was beyond the scope of its responsibility and had difficulty in meeting delivery schedules; (4) SEIC identified changes in the NAS plan that could raise modernization costs from $15.8 billion to $24 billion by the year 2000; and (5) FAA did not have sufficient technical support, controller, or maintenance work forces to implement transition to the future system. GAO believes that a redefined NAS plan would enhance future implementation decisions and permit resetting priorities due to the significant increase in projected funding needs.