the compresibility of air becomes significant wgen air flows at what speed?

The compressibility of air becomes significant when air flows at speeds approaching or exceeding the speed of sound, which is approximately 343 meters per second (1235 km/h or 767 mph) at sea level. At these high speeds, the density and pressure of the air can change significantly, leading to compressibility effects such as shock waves and changes in temperature.

Mach 0.3