I know that ICAO Annex 2 'Rules of the air' states rules such as general rules, visual flight rules, instrument flight rules, etc. And aircraft should fly in accordance with either visual flight rules or instrument flight rules, and that is VFR and IFR. If aircraft fly in accordance with visual flight rules, that must be VFR.

But apart from these rigid rules, I image VFR as a flight that should fly with outside visual reference and have responsibility to avoid and separate with other obstacles or aircraft and IFR as a flight referring to instrument to avoid and be separated with other obstacles.

I tried to find more kind explanations(rather than ICAO ANNEX 2) about it like I stated above, but failed. Of course, I could find many documents or information like wikipedia, but there was no official source such as ICAO or FAA documents.

Could you give me some source that define VFR or IFR like as I stated above?

  • 1
    $\begingroup$ To be clear, you're looking for the meanings of Visual Flight Rules and Instrument Flight Rules, not the meteorological conditions that lead one to pick one over the other, correct? $\endgroup$
    – FreeMan
    Mar 20, 2019 at 14:12
  • 2
    $\begingroup$ This may be a nice summary of what you are looking for. In terms of the FAA there are lots of regulations that define how VFR and IFR operations occur, what you are aloud to do, what ATC will provide to you, what kind of certification you need and what the aircraft must be equipped with to conduct such operations. Its not one specific regulation so much as a combination of many. $\endgroup$
    – Dave
    Mar 20, 2019 at 15:00
  • $\begingroup$ @Pondlife, that question's answer basically points to the ICAO annex 2, which is mentioned in this question as not understandable for the asker, so I would consider it not a duplicate. $\endgroup$
    – Jan Hudec
    Mar 20, 2019 at 21:10
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    $\begingroup$ @JanHudec I see your point and perhaps the question is just unclear. The OP asks for "official" sources like FAA and ICAO but isn't very clear on why they aren't "kind" enough. It might be helpful for the OP to explain exactly what's unclear from the Annex 2 rules, otherwise I'm not sure what we can answer exactly. Just my two cents, as always. $\endgroup$
    – Pondlife
    Mar 21, 2019 at 3:06
  • $\begingroup$ I'm sorry for those of who feel my question is duplicate. The reason of why I ask similar question is I was failed to find official data that states VFR as a flight that pilot have to see outside and responsibility to separate with other aircraft or obstacles. Many unofficial information such as Wikipedia, personal blog, etc say it but not FAA or ICAO documents. Of course, I know that VFR should be operated in VMC but no documents directly state that VFR flight have responsibility to separate by itself. $\endgroup$
    – Min
    Mar 21, 2019 at 12:54

1 Answer 1


tl;dr The basic differences between IFR and VFR involve weather, required equipment, filing flight plans and getting a clearance, and the altitudes flown.

Your question indicates that you may not know that there is a difference between Visual Meteorological Conditions (VMC) and Visual Flight Rules (VFR). Likewise between Instrument Meteorological Conditions (IMC) and Instrument Flight Rules (IFR). You can be flying under Instrument Flight Rules in VMC—the airlines do this on most flights. It is not wise to fly VFR into IMC—a huge percentage of general aviation accidents happen because of that.

One source of the definitions is the FAA publication Pilot Controller Glossary, although they sort of presume you already know the concept.

INSTRUMENT FLIGHT RULES− Rules governing the procedures for conducting instrument flight. Also a term used by pilots and controllers to indicate type of flight plan.

INSTRUMENT FLIGHT RULES[ICAO]−A set of rules governing the conduct of flight under instrument meteorological conditions.

INSTRUMENT METEOROLOGICAL CONDITIONS− Meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling less than the minima specified for visual meteorological conditions.

VISUAL FLIGHT RULES− Rules that govern the procedures for conducting flight under visual conditions. The term “VFR” is also used in the United States to indicate weather conditions that are equal to or greater than minimum VFR requirements. In addition, it is used by pilots and controllers to indicate type of flight plan.

VISUAL METEOROLOGICAL CONDITIONS− Meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling equal to or better than specified minima.

The FARs only indirectly define IFR but you can get the rest of the definitions from the FARs.

§1.1 General definitions.
IFR conditions means weather conditions below the minimum for flight under visual flight rules.

§91.155 Basic VFR weather minimums. (a) Except as provided in paragraph (b) of this section and §91.157, no person may operate an aircraft under VFR when the flight visibility is less, or at a distance from clouds that is less, than that prescribed for the corresponding altitude and class of airspace in the following table:

The table lists the visibility and clearance from clouds in different kinds of airspace that you need in order to fly under visual flight rules. If the weather is less than the minimums, then you need to fly under Instrument Flight Rules.

You can get an idea of the differences by reading CFR PART 91—GENERAL OPERATING AND FLIGHT RULES Subpart B—Flight Rules

  • $\begingroup$ Thanks for your sincere answer. Now, I know VFR, VMC, IFR and IMC. VFR 'are' set of rule's' pilot should comply. I'm looking for source that VFR pilot is responsible to see outside to avoid collision. Could you let me know that source? $\endgroup$
    – Min
    Mar 21, 2019 at 13:24
  • $\begingroup$ @Min All pilots, whether flying IFR or VFR are required to see-and-avoid other aircraft. CFR §91.113 Right-of-way rules: Except water operations. (b) General. 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. $\endgroup$
    – JScarry
    Mar 21, 2019 at 14:05
  • $\begingroup$ THANKS!!! It's what I am looking for! $\endgroup$
    – Min
    Mar 22, 2019 at 12:36

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