Sec. 91.821 - Civil supersonic airplanes: Noise 
      limits.
      Except for Concorde airplanes having flight time before January 1, 
      1980, no person may operate in the United States, a civil supersonic 
      airplane that does not comply with Stage 2 noise limits of part 36 in 
      effect on October 13, 1977, using applicable trade-off provisions. 
        
       
  
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