Definition
A unit of speed equal to one statute mile (5,280 feet) traveled in one hour. In aviation, it is one of three speed units a pilot may encounter, alongside knots (nautical miles per hour) and kilometers per hour. One statute mile per hour equals approximately 0.87 knots.
Plain English
How many regular road-distance miles you cover in an hour. The same mph you see on a car speedometer.
Context Anchor
Seen on some older airspeed indicators, aircraft manuals, and performance information where speeds are given in miles per hour instead of knots.
Derivation
Statute' comes from Latin statutum, meaning 'something laid down by law.' The statute mile was the legal mile fixed by English law at 5,280 feet, to distinguish it from the nautical mile, which is based on the geometry of the Earth. So a statute mile is the 'legal' or 'land' mile, the one used on roads.
Why Pilots Care
Aircraft performance and navigation primarily use knots, but some references list speeds in statute mph; mixing the units can produce large errors in calculations.
Intuition Check
Do not read statute here as meaning a rule or regulation to follow. In this term, statute identifies the regular land mile of 5,280 feet, not a nautical mile.
Example Sentence 1
The older airspeed indicator in the trainer was marked in mph, so the pilot mentally converted 100 mph to about 87 knots before comparing it to the performance chart.
Example Sentence 2
The airplane's maximum speed in level flight is listed as 135 statute miles per hour in the performance section.