What do you mean by Stage 2 or Stage 3?

The FAA, under Federal Aviation Regulation, Part 36, designates every aircraft either Stage 1, 2, or 3 based upon noise limits and testing.  Stage 3 aircraft are generally the newest, quietest aircraft built since the mid 1980’s.   Examples of Stage 3 aircraft are the Boeing 757-200, 737-700, the McDonnell-Douglas MD80, as well as Airbus’ A320.  Stage 2 aircraft were the earlier generation of these same or similar aircraft that did not meet the more stringent noise levels required by Stage 3 of Part 36.  Stage 2 aircraft can also be hush-kitted or re-engine to be certified as Stage 3 aircraft.  Some aircraft that have been hush-kitted to meet the Federal Stage 3 standard include the Boeing 727 series, 737-100/200, DC-8, and DC-9 series aircraft.