as a result, the principal data source included 127 in depth pilot survey responses
and 43 semi-structured interviews of one to two hours in length. Interviews were
conducted via telephone or skype, were digitally recorded and, depending on content,
were either fully or partially transcribed. In addition, dozens of emails were exchanged
with respondents over time to clarify discrepancies, expand discussion, and amplify
points of interest. A wide range of secondary sources also was also used, such as
Congressional hearings, Government Accounting Office (GAO) studies, Federal
Aviation Administration (FAA) documents, National Transportation Safety Board
Figure