Base level

This regulation establishes how operators calculate their "base level"—essentially a quota for how many Stage 2 (noisier) airplanes they're allowed to operate under the noise reduction program.

For U.S. operators, the base level equals the number of Stage 2 aircraft they had on their operations specifications on any single day they choose between January 1, 1990, and July 1, 1991. This number increases when they return Stage 2 aircraft to service, purchase them under specific provisions, or acquire base level from another operator. It decreases when they transfer base level along with aircraft to someone else.

Foreign air carriers follow similar rules, using their U.S. operations specifications from that same 1990-91 period.

New entrants have no base level, meaning they start with zero Stage 2 aircraft allowance. This matters because your base level determines how many Stage 2 aircraft you can operate under the phase-out program.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*