What does \"visual line of sight\" actually require?

Know what VLOS is defined to require — which is more than seeing the aircraft — know when the pilot may look away, know who else may hold the sight, and know the two regimes that exist because VLOS is not required there.

"Visual line of sight" is the condition most of the Regulations are organised around, and it appears in almost every other lesson. It is also defined, and the definition is a test with three parts. CAR 900.01

• You know who is operating and whether a visual observer is part of the operation, because the sight may be held by either. CAR 901.11 AIM 3.6.1
• You know whether the operation is a plain VLOS operation or an extended VLOS or sheltered operation, because those have their own section. CAR 901.74

VLOS is defined as unaided visual contact at all times with the remotely piloted aircraft that is sufficient to be able to: maintain operational control of the aircraft; know its location; and scan the airspace in which it is operating to detect and avoid other aircraft or objects. CAR 900.01

Three capabilities, joined by "and". Keeping the aircraft in view while being unable to scan the airspace around it does not satisfy the definition, which is why the definition is worth learning before the rule that uses it. CAR 900.01

No pilot shall operate a remotely piloted aircraft system unless the pilot or a visual observer has the aircraft in visual line-of-sight. CAR 901.11

The exceptions are listed in the same section: an operation referred to in paragraph 901.62(b) or (c) conducted in accordance with Division V — that is, an extended VLOS or sheltered operation — or an operation referred to in section 901.87 conducted in accordance with Division VI, or an operation conducted in accordance with a special flight operations certificate — RPAS. CAR 901.11 CAR 901.62 CAR 901.87

So VLOS is the default condition, and every route out of it is named. CAR 901.11

The AIM is explicit about the boundary, and it is subtler than it first appears.

A pilot may take their eyes off the aircraft for brief moments to operate the control station or perform other flight-critical tasks without being considered to have lost VLOS. But if a task will require an extended loss of visual contact, the pilot should use a visual observer or land the aircraft until the task is complete. AIM 3.2.1

Set against that, the same page states that losing sight of the aircraft behind buildings or trees, or into clouds or fog, is strictly prohibited even for a short period. AIM 3.2.1

The two statements are consistent, and the distinction between them is the thing to learn:

Situation	Result
The pilot looks down at the control station for a moment	Not a loss of VLOS AIM 3.2.1
The aircraft passes behind a building for a moment	Prohibited AIM 3.2.1
A task requires extended loss of visual contact	Use a visual observer, or land first AIM 3.2.1

The allowance is about the pilot's attention; the prohibition is about the aircraft being obscured. Where the pilot is looking and whether the aircraft can be seen are different questions, and only the first is forgivable. AIM 3.2.1

VLOS can be maintained by the pilot keeping the aircraft in sight for the duration of the flight, or by using one or more trained visual observers. The aircraft must remain in VLOS with the pilot or at least one visual observer at all times. AIM 3.2.1

Note what that means in practice: the pilot is not required to be the person seeing the aircraft, but somebody must be, continuously. AIM 3.2.1

The AIM separates them, and the separation explains several other rules.

• Visual line of sight — the pilot keeping an unaided visual reference with the aircraft throughout the flight. AIM 3.2.1
• Radio line of sight — a function of the command and control data link between the control station and the aircraft, for the purpose of managing the flight. AIM 3.2.1

They share a foundational idea — an imaginary line between the pilot, through the control station, to the aircraft, unimpeded by obstacles or excessive distance — but they have different applications. A flight can have one without the other. AIM 3.2.1

The maximum range for VLOS is not prescribed by regulation. Pilots are required to determine the maximum distance the aircraft can travel away from them before it becomes a hazard. AIM 3.2.1 CAR 901.28

That is a planning obligation with no number attached, which makes it easy to skip and hard to defend afterwards: the answer depends on the aircraft's size, the light, the background and the pilot's own eyesight. CAR 901.28

"BVLOS operation" is itself a defined term, and the definition carries two exclusions. It means an operation of a remotely piloted aircraft that is not in visual line-of-sight — but it does not include an extended VLOS operation or a sheltered operation. CAR 900.01

Read that against the paragraph below, because it is where a question sets its trap: an operation flown outside VLOS with a visual observer maintaining unaided contact with the airspace in which the aircraft is operating is an extended VLOS operation, and the definition says so in as many words. It is not a BVLOS operation, whatever the distance between the aircraft and the pilot. CAR 900.01

Extended VLOS and sheltered operations exist because VLOS is not required for them. Their own section requires that the pilot and control station are located at the site set aside for take-off, launch, landing or recovery at the time of those activities; that the aircraft is at a distance of not more than two nautical miles from the pilot, the control station and the visual observer at any time during the flight; and that the operation is conducted at least 100 feet (30 m) horizontally from any person not involved. CAR 901.74

Read the second condition closely: two nautical miles is a limit on the operation, and it is measured from the pilot, the control station and the visual observer — all three. CAR 901.74

Question	Answer
What must VLOS let you do?	Maintain operational control, know the location, and scan the airspace CAR 900.01
Who must hold it?	The pilot or a visual observer CAR 901.11
Is a glance at the control station a loss of VLOS?	No, if brief AIM 3.2.1
Is the aircraft passing behind a building acceptable?	No, not even briefly AIM 3.2.1
Extended loss of visual contact	Use a visual observer, or land AIM 3.2.1
Maximum VLOS range	Not prescribed; the pilot must determine it CAR 901.28
Extended VLOS or sheltered operation	Two nautical miles maximum from the pilot, control station and observer CAR 901.74

Warning "I could still see it" and "I had it in sight" are not the same claim as the definition. VLOS requires contact sufficient to scan the airspace for other aircraft, so a flight where the aircraft is visible but the airspace around it is not being watched fails the definition even though the aircraft never left the pilot's view. CAR 900.01

Symptom	Likely cause	What to do
Your aircraft will pass behind a building on the route	Losing sight behind obstacles is prohibited even briefly	Re-plan the route AIM 3.2.1
You need both hands on the control station for a while	A brief glance is allowed; an extended loss is not	Use a visual observer or land AIM 3.2.1
You can see the aircraft but not the sky around it	The definition requires scanning the airspace	Reposition or reduce distance CAR 900.01
You are alone with an FPV feed and no observer	FPV does not satisfy unaided visual contact	Add a visual observer AIM 3.2.1
You never worked out a maximum distance	The AIM requires you to determine it	Do the assessment before flying CAR 901.28
Your extended VLOS operation drifts past two nautical miles	The limit applies at any time in the flight	Keep inside it CAR 901.74

Practise: Rpas visual line of sight

Practise: Extended VLOS and sheltered operations

Practise: Basic operations division iv application

• CAR 900.01 — Interpretation
• CAR 901.11 — Visual Line-of-sight
• CAR 901.28 — Operating Limitations
• CAR 901.62 — Application
• CAR 901.74 — Extended VLOS Operations and Sheltered Operations
• CAR 901.87 — Application
• AIM RPA 3.2.1 — Line-of-sight
• Consolidation: CARs current to 2026-09-21