CREATE TABLE "table1_18047346_4" (
  "rank" real,
  "airport_name" text,
  "location" text,
  "iata_code" text,
  "passengers" text,
  "pct_chg_2009_10" text
);

Question: If the passengers are 15,505,566, what is the iata code?
SQL: SELECT "iata_code" FROM "table1_18047346_4" WHERE "passengers"='15,505,566';

Question: If the location is Chicago, Illinois, what is the airport name?
SQL: SELECT "airport_name" FROM "table1_18047346_4" WHERE "location"='Chicago, Illinois';

Question: If the amount of passengers is 15,505,566, what is the %/chg. for 2009/10?
SQL: SELECT "pct_chg_2009_10" FROM "table1_18047346_4" WHERE "passengers"='15,505,566';