High Level Airspace

High-level airspace is the controlled airspace above FL180 in Canada — Class A airspace. All operations in high-level airspace are conducted under IFR, regardless of weather conditions, and all aircraft must be under ATC control.

Class A Requirements

  • IFR-rated pilot and IFR-equipped aircraft
  • ATC clearance required before entering
  • All aircraft on IFR flight plans
  • Transponder with altitude encoding (Mode C or Mode S) required
  • Navigation equipment appropriate for the route

Transition Into High-Level Airspace

When climbing through FL180, set the altimeter to 29.92 inHg and switch from altitude reporting (feet MSL) to flight level reporting. Notify ATC when you complete the transition. Descending through FL180, set QNH as provided by ATC.

Related Terms

See also: Classification of Airspace, Flight Level, Altimeter Setting.