"See and Avoid" is recognised as a method for avoiding collision when weather conditions permit and requires that pilots should actively search for potentially conflicting traffic, especially when operating in airspace where all traffic is not operating under the instructions of ATC.
"When weather conditions permit, regardless of whether an operation is conducted under instrument flight rules or visual flight rules, vigilance shall be maintained by each person operating an aircraft so as to see and avoid other aircraft. When a rule of this section gives another aircraft the right-of-way, the pilot shall give way to that aircraft and may not pass over, under, or ahead of it unless well clear."
The high speed of modern commercial aircraft has called into question the adequacy of the "see and avoid" principle for such traffic and an article published over 10 years ago by the Flight Safety Foundation (FSF) questions its relevance. Reference to it It is rarely found in the Operating Procedures of most air carriers since they operate mainly in Controlled Airspace.
However, it is important to slower aircraft, especially in any Class 'G' uncontrolled airspace and in busy airspace where ATC does not providing separation to VFR traffic.
Limitations of the See-and-Avoid Principle, which concludes that "The see-and-avoid principle in the absence of traffic alerts is subject to serious limitations. It is likely that the historically small number of mid-air collisions has been in a large part due to low traffic density and chance as much as the successful operation of see-and-avoid".