What does AOE on the sectional chart mean?
It stands for "Airport Of Entry" (see VFR Terms) In other words there are customs facilities there. 


  All civil, private aircraft entering the U.S. must first land at an
  airport of entry before continuing to their destinations, unless other
  arrangements are made with U.S. CBP. Advance notification must be
  provided electronically to CBP by means of the eAPIS. See the APIS
  section for more information.
  (source)


To my knowledge this is also common for international operations outside of the US/FAA jurisdiction although im not sure how its marked on various maps elsewhere.