CREATE TABLE table_204_163 (id DECIMAL, "airline" TEXT, "icao" TEXT, "iata" TEXT, "callsign" TEXT, "commenced\ operations" DECIMAL)

how long between the operations first commenced and the last airline to commence operations ?
SELECT (SELECT "commenced\noperations" FROM table_204_163 ORDER BY "commenced\noperations" DESC LIMIT 1) - (SELECT "commenced\noperations" FROM table_204_163 ORDER BY "commenced\noperations" LIMIT 1)
SELECT (SELECT "commenced\noperations" FROM "table_204_163" ORDER BY "commenced\noperations" DESC NULLS LAST LIMIT 1) - (SELECT "commenced\noperations" FROM "table_204_163" ORDER BY "commenced\noperations" NULLS FIRST LIMIT 1)