In general aviation, scud running is a practice in which pilots lower their altitude to avoid clouds or instrument meteorological conditions (IMC).
This practice is widely accepted to be dangerous, and has led to death in many cases from pilots flying into terrain or obstacles, such as masts and towers, normally referred to as controlled flight into terrain, or CFIT;[1] however, even instrument-rated pilots sometimes elect to take the risk to avoid icing or embedded thunderstorms in cloud, or in situations where the minimum instrument altitudes are too high for their aircraft.
"[2] A procedure under instrument flight rules (IFR), called a contact approach, is often referred to as a form of "legalized" scud running.
[4] In Canada, the visibility and altitude requirements are similar to those in the U.S., but most controlled airspace outside of terminal areas bottoms out at 2,200 feet (670 m) Above Ground Level (AGL), so there is more room to scud run legally.
However, outside of airport control zones and major terminal areas, controlled airspace typically begins at 1,200 feet (370 m) above ground level; below that is uncontrolled (class G) airspace, where (at that altitude) a pilot is required only to remain clear of clouds and to maintain 1 statute mile (1.6 km) visibility.