In regards to what John Farley said... under Transport Category airplanes, they must be free from any aeroelastic effects under all configurations and design conditions by an increase of 15 percent in equivalent airspeed at both constant Mach number and constant altitude... among a few other requirements.
Part V - Airworthiness Manual Chapter 525 - Transport Category Aeroplanes - Transport Canada
The Transport Canada Reg is essentially an exact copy of the FARs. Reference FAR 25.629.