CREATE TABLE table_60830 ("Aircraft" TEXT, "Introduced" FLOAT, "Retired" TEXT, "Seating" TEXT, "Notes" TEXT)

When was the aircraft introduced that could seat 115 people?
SELECT AVG("Introduced") FROM table_60830 WHERE "Seating" = '115'
SELECT AVG("Introduced") FROM "table_60830" WHERE "Seating" = '115'