Fairies can travel at Mach 49.
Data and assumptions:
In Act II, Scene 1 of Midsummer Night's Dream, when sent on a mission by Oberon, Puck says that he will "put a girdle round about the earth
In forty minutes."
Now, as a girdle goes around the widest point of a person, we can assume that Puck is saying that he can do an equatorial circumnavigation of the Earth in 40 minutes. The equatorial circumference of the earth is pretty darned close to 24900 miles, or 40075 km. (The polar circumference is 40036, by the way. They attempted to define the kilometer as 1/10000 the distance from the equator to the pole, but some error crept in, and they didn't hit it quite. Still, as an off-the-cuff number to remember, "40000 km circumference" is a fine approximation.)
24900 in 40 min is 37350 mph, which is just about Mach 49. Therefore, fairies can travel at Mach 49 sustained for forty minutes.
Context creeps in this petty pace from day to day. QWP.