- The cruising speed of Boeing 777 is ~900km/h, ie, 250m/s;

- The cruising distance from Beijing to NYC is ~11,000km;

- The time is ~ 12 hrs.

- If the time were 2hrs, the speed should be 250*6 = 1500 m/s, which is 1500/330 > 4 times of sonic speed in the air.

But, I am not sure what the sonic speed is at an altitude of 11,000 m.

Anyone can shed light on this?