This  report  presents  statistical  information  on  aircraft  activity  and  passenger  and  cargo traffic at California airports.  Four main topics are considered: passenger enplanements, air travel origin and destination (O-D) patterns, aircraft operations, and air cargo.  In each case, we present data  for  the  state  as  a  whole,  major  regions  within  the  state,  and  major  airports  within  each region.  Most of the data are compiled on an annual basis for the years from 1980 to 1996.Enplanement  activity  in  California  is  heavily  concentrated,  with  a  handful  of  airports accounting for the vast majority of the state total.  The concentration has increased between 1980and   1996,   during   which   time   California’s   enplanement   growth   mirrored   national   trends. However,  within  the  multiple  airport  systems  of  the  San  Francisco  Bay  Area  and  Southern California there is evidence of dispersion, as San Francisco International (SFO) and Los Angeles International (LAX) airports have lost market share to their smaller competitors.