VFR versus IFR


What are the parameters that determine flying IFR versus VFR. Is it the type of aircraft, e.g. jet versus piston? Is it above a certain altitude? I assume passing through an ADIZ makes it mandatory, but today a plane came into our local airport (KDMW). Since the operator is located in the Washington DC area, I think he may have come from KGAI (Gaithersburg Montgomery airport), but there is no track in flightaware meaning that he must have flown VFR.


Pilot has to be rated IA to flying IFR. After that is established, then weather takes part in deciding whether to fly based on IFR or VFR.

ADIZ does NOTrequire a pilot to fly under IFR.

Just so we are clear on some terms.

IFR = Instrument Flight Rules.
VFR = Visual Flight Rules.

NEITHER have anything to do with weather outside your window, only the rules the pilot has to abide by when he or she flies.

For ADIZ, you are required to be “squawking and talking” whether you are flying under VFR or IFR.

While I can fly here in MS without talking to a soul and without a transponder from my UNcontrolled airport, that privilige was taken away from the folks that live in the ADIZ area. They must be talking to ATC and be assigned a descrete transponder code BEFORE wheels leave the ground or BEFORE entering the ADIZ.

This is done under VFR or IFR irregardless of the weather outside. IFR just makes it a little bit easier navigation and meets the ADIZ requirments for entry.

Please see discussions.flightaware.com/view … light=adiz for further discussion on the ADiZ

(who is planning a flight to DMW if freezing level stays high enough)


I am no ATP, but here is the basics as I know them.

Instrument Flight Rules are about a method of flying, control, and navigation designed to eliminate crashes. Not that it always works, but if you do it right, you can fly without seeing outside (until justs before landing), just by using instruments. Scheduled airline traffic is almost exclusively flown IFR, I don’t know if its a government rule or an airline/insurance one. (someone will likely straighten me out on this one)

Instrument Meteorological Conditions (IMC) is weather that prohibits VFR flying due to lack of visibility. Definition of IMC varies by type of airspace and time of day, but only a few bold types would argue it is too restrictive. Most IFR flight is actually in Visual Conditions, but under IFR rules.

Sometimes, but rarely, IFR will be required without IMC. Instead VFR planes can be required to use radar services and stay in contact with ATC which will likely restrict them to a vector and altitude which they must follow unless the direction is unsafe. Flight Aware usually tracks planes using radar service under VFR.

All flight above 18,000 feet is in class A airspace and is required to be IFR unless waivered (I think gliders can get waivers, as well as some balloons). Even if its a clear day.

To qualify for IFR flight, the PIC and the plane must meet standards. The pilot must have an IFR rating, and the plane must be IFR certified. The training for pilots includes training for high altitude operations above 18,000 feet, as well as all the rules and methods to fly in IMC and other stuff.

The certification for the plane is a long list, but generally the airframe must be up to it (mostly lightning protection), as well as the plane needing a good deal of certified instruments that are checked on a schedule. The instruments required are a bare bones minimum to keep us safe in the clouds, and most of us like more than is required (redundancy, and better stuff like GPS and an autopilot). Basically, its instruments for position and vector and attitude along with a bunch of radios that guide us from start to finish along paths from beacon to beacon until we get close enough to see the airport and land.


Thanks for the information. The plane I mentioned in my initial post was a small jet. The reason the question came up for me is that the local airport is tower-less but is getting an increasing amount of jet traffic. In this particular instance, there were winds coming from the west with occasional gusts out of the northwest. The sole runway runs northwest - southeast (designation is 16-34). In the morning planes had been taking off to the south, but while i was there about 1300 the winds were shifting & some local guys were taking off to the north & a corporate twin-engine piston plane came in to land on 34, I happened to look north and I saw a headlight and it was the small jet landing on 16. There was never any danger of collision, but it made me wonder where the jet was coming from, so when I got home I checked flightaware and he wasn’t listed. Perhaps he has his tail number blocked, although I can’t see why a corporation would block. I just assumed that a jet, especially a corporate, would be flying IFR - but I guess they don’t necessarily have to?


As long as it was flying below 18,000 feet and in Visual Meteorological Conditions (VMC), they do not need to fly under an IFR flight plan (which is what FlightAware generally captures). On short repositioning flights, jets often do not.


Ive always thought it was mainly Airline aircraft that flew under IFR rules,

IFR is about comunicating with ATC, while VFR is more basically navigating yourself,

Is this the basics? or do i have to go back to the books???


In GENERAL, less than 3 miles visibility with a ceiling of 1000 AGL or less requires an IFR flight plan in order to operate an aircraft.

However, in Class B, you can be clear of clouds with 1 mile vis and be legal for Special VFR if they allow it - most real busy Bravos do not.

In Class G airspace, the limits can be 1 mile vis and clear a clouds.


True IFR requires communication with ATC, but they provide little navigation. Not true that mainly airline aircraft fly IFR. Although airlines do fly IFR, a large portion of General Aviation also fly Instrument Flight Rules. The exact same service is available for all rated pilots and aircraft.

Both the VFR and IFR pilot are responsible for their own navigation, the difference is the VFR pilot navigates to visual reference like landmarks and the IFR pilot navigates with radio navigation aids like VOR’s and GPS.


I dunno what you mean about ATC providing little navigation. When I fly IFR they are constantly telling me where to go, and at what altitude. In fact, except when I lost comms with them, I can’t remember them not telling me where to go.


The difference, in a nutshell, is who provides separation from other aircraft. VFR aircraft see and avoid other traffic. IFR aircraft are provided separation from other known traffic by ATC.

Disclaimer: this is a very, very basic description. Your mileage may vary.


IFR aircraft are provided separation from other IFR traffic. You were correct to add “known” traffic, as ATC will advise you on VFR traffic using flight following. When in visual conditions, even if you are on an IFR flight plan, it is still the pilot’s responsibility to see and avoid.


You might want to add “also unknown traffic squawking mode C and 1200 not using flight following”.

ATC will say, Sundowner 1943L traffic 2:00 2500 unverified.



In addition to traffic separation, ATC has the responsibility to provide terrain avoidance to aircraft flying IFR. They have a minimum vectoring altitude for every sector that they use in order to keep airplanes out of the dirt. When a pilot is in visual conditions, even flying IFR, they also have a responsibility to maintain visual terrain avoidance.


Depending on where you fly, they might provide a plethora of navigation assistance, but they are not required to especially if there is no radar coverage.


The one last requirement for ATC separation is from other airspace.


Can you clarify?

IFR, airspace is “transparent”.

You will be routed around hot MOA’s, SUA’s and TFR’s on IFR, but insofar as airspace classes, once you receive your clearance, doesn’t matter if you are in A, B, C, D or E, as you have been cleared from you picking up your clearance.

VFR, it’s the pilots responsibility, NOT the controllers responsibility for obtaining and receiving airspace clearances.



I guess that post was pretty vague. This requirement is mostly hidden as far as the pilot is concerned, but a controller is responsible to separate aircraft from other aircraft, terrain/obstacles and airspace. A controller is responsible for a certain sector of airspace and must not allow aircraft in his sector to penetrate another sector without notifying that particular sectors controller. That’s where we get handoff’s. Although this might not seem to directly effect the pilot, it might help explain why ATC might deny a request, or help to anticipate routing changes.


Still need a little help with this…

If I get cleared as filed, I am under the impression that airspace is mine from point A to point B with my safety bubble following all around me. I am cleared through all airspace, all center sectors at my assigned altitude (assuming no popup TFRs or unusual events)

If a center controller for some reason doesn’t or isn’t able to make a land line call or whatever they do to transfer my handling, that voids my clearance based on what you are posting? Bear with me as you do have me confused, and I am ntwo years new in the IFR world and still learning.

For example, I am trundling along from KMBO (Madison MS to L31 (Covington LA) IFR flight plan, filed direct, and I am talking to Memphis Center.

If Memphis for some reason can’t get a hold of Houston Center for my handoff, are you saying that I can expect a reroute and cannot enter the Houston center sector which shuts down my entire flight as there is no way to L31 without going through Houston center?

I have flown under no radar conditions where I report via radio, so I don’t think you mean this?

Not quite so sure that has ever happened to me and really kinda sounds far fetched, unless I am totally misunderstanding your post.

For VFR traffic, there is no clearance and the above doesn’t apply at all since flight following is advisory in nature and workload permitting.




Basically, it is only the initial part of your clearance that means much even though the clearance may read cleared as filed. In GA IFR flying, it is normal to get one or more amendments/revisions to your flight plan as you fly longer distances. So for example, you could get an initial clearance to fly at 5000’ on an airway that later goes over 10,000’ mountains because the first segment has a a 4000’ MCA. As you get closer to the mountains, ATC will call you and give you an amended clearance at 12,000’+ for appropriate terrain avoidance (2000’ above obstacles). As you come into a busy sector, they will often give you an amended clearance for traffic avoidance. When I fly through Los Angeles, they often take me way east to avoid LAX traffic, but sometimes I get a clearance right over the top of LAX. In other cases you might request an amended clearance (usually in the form of direct to XXX) that they can’t give you because of traffic, terrain or active airspace. So I’ve been told that they can give me direct LAX if I will fly at 11,000’, otherwise they will need to reroute me east around LAX if I want to stay at my current altitude. Or they can’t give me direct XYZ because the military airspace is currently hot.

About the only situation that I can think of where you could actually fly a full cleared as filed flight plan would be total radio failure with no back-ups. Even then, you would probably land somewhere short of your destination airport if you are in VFR conditions. As one controller explained to me, when you are NORDO (no radio), they just watch you on radar and clear the airspace around you so you can do almost anything.


Hey CAFlier,

Fully understand what you are saying as that’s happened to me, getting amendments for air traffic flow considerations. Dummy me, tried filing direct from Bluefield WV to Westminster MD. Needless to say, as I was getting closer to Martinsburg, got that call from center, 1943L, amendment to your clearance, ready to copy. The amendment was nothing more then tossing me on the airways.

In THEORY, when you are cleared as filed, you are cleared from point A to point B. As you deftly brought up, the real world presents a different picture :slight_smile:

Of course, when you fly down my way, you get questioned why not file /G. During my IFR training, several times, I was queried if I would rather go direct.

Magnetoz is saying something very, very different and I am trying to get a clarification.

FROM WHAT I understand, Magnetoz said that an aircraft cannot enter another sector’s airspace should the originating sector cannot handoff to the next sector. (see my example in my prior post) That’s the part I am questioning.