"Through our investigations, we recognized that a better
understanding of airline code-sharing arrangements and their role
in aviation safety was needed, so we held a symposium last
October... We found that there is no universal type of
code-share. Whether it's a code-share partnership between a
domestic main line carrier and regional air carrier, or two
domestic main line carriers, or domestic and international
carriers, these are complex relationships. Many mainline carriers
have multiple regional partners, and some regionals fly for several
mainline carriers."
Source: In a keynote address Wednesday to
the American Bar Association's Forum on Air and Space Law 2011
Update Conference, NTSB Chair Debora A.P. Hersman addressed the
issues