Visual flight and instrument flight: VFR and IFR explained simply

It’s a gray autumn morning, and the clouds hang low over the runway. The airliners keep coming out of the murk every minute or so, but the Cessna you saw flying traffic patterns last weekend stays in the hangar. The reason is no coincidence but a set of rules: visual flight (VFR) and instrument flight (IFR). This guide explains the difference, the most important weather limits and flight levels – and what you notice of it at the fence, on the live map and on the aviation radio.

VFR and IFR: the short answer

VFR (Visual Flight Rules) are the rules for visual flight. The crew navigates by sight of terrain, roads, rivers and the horizon and is itself responsible for keeping clear of clouds, obstacles and other aircraft. The principle is called “see and be seen.” For it to work, the weather has to meet certain minimum values for visibility and distance from clouds.

IFR (Instrument Flight Rules) are the rules for instrument flight. The aircraft flies by instruments and published procedures – departure routes, airways, approach procedures. In controlled airspace, air traffic control issues clearances and separates IFR flights from each other. In return, an IFR flight may also fly in and above the clouds. The prerequisites are suitably equipped aircraft, correspondingly qualified pilots and, in most cases, a flight plan.

In Europe, both sets of rules are laid down in the Standardised European Rules of the Air (SERA), EU Implementing Regulation 923/2012. National authorities can deviate in places or add details.

Flight rules and weather: VFR/IFR versus VMC/IMC

A common misunderstanding: VFR doesn’t mean “good weather” and IFR doesn’t mean “bad weather.” The technical language separates the two cleanly.

• VFR and IFR are the flight rules under which a flight is conducted.
• VMC (Visual Meteorological Conditions) and IMC (Instrument Meteorological Conditions) describe the weather: VMC exists when flight visibility and distance from clouds reach the visual-flight minimums; IMC is everything below that.

It follows that a VFR flight needs VMC. An IFR flight can take place in VMC and in IMC. The Airbus passing over your spot under a cloudless sky is still flying IFR – with a flight plan, clearance and an assigned route. Whether an airport has “VMC” or “IMC” on a given day, by the way, you can read yourself from the weather report; how that works is explained in the guide Reading METAR and TAF.

	Visual flight (VFR)	Instrument flight (IFR)
Navigation	by sight, supplemented by chart and navigation devices	by instruments and published procedures
Separation from other traffic	crew keeps it itself, with support depending on airspace	separated by air traffic control in controlled airspace
Weather	only with minimum visibility and cloud clearance (VMC)	also in clouds and poor visibility (IMC)
Flight plan	mandatory only in certain cases	generally mandatory
Typical users	private and training flights, gliding, sightseeing flights, many helicopters	scheduled and charter traffic, business aviation, cargo
Cruising levels above 3,000 ft	full thousands plus 500 feet	full thousands

The weather limits for visual flight

SERA sets minimum values for VFR for flight visibility and distance from clouds. They depend on altitude and airspace class. Simplified, it looks like this:

Altitude band	Airspace	Flight visibility	Distance from clouds
from 10,000 ft above sea level	B to G	8 km	1,500 m horizontal, 1,000 ft vertical
below 10,000 ft, above 3,000 ft MSL or 1,000 ft above ground	B to G	5 km	1,500 m horizontal, 1,000 ft vertical
up to 3,000 ft MSL or 1,000 ft above ground (whichever is higher)	B to E	5 km	1,500 m horizontal, 1,000 ft vertical
up to 3,000 ft MSL or 1,000 ft above ground	F and G	5 km	clear of clouds, surface in sight

For the bands near the ground, the rules allow relaxations if the competent authority permits them: in airspace F and G, flight visibility during the day can be reduced to as low as 1,500 meters for slow aircraft (no more than 140 knots indicated airspeed). Where the transition altitude is below 10,000 feet, flight level 100 takes the place of the 10,000-foot limit. Airspace A is closed to visual flights.

Which airspace classes lie above your spot and how to recognize them on the chart is shown by the article Airspaces C, D, E, G and control zones.

The special rule for control zones

Around airports with instrument flight operations lies a control zone (CTR). For it there is an additional threshold: without special clearance, a VFR flight may neither take off nor land there, nor enter the traffic pattern or the aerodrome traffic zone, if the reported cloud base is below 1,500 feet or the ground visibility is below 5 kilometers.

Below that, only Special VFR remains. It requires clearance from air traffic control, and its own limits apply:

• generally only during the day, with exceptions for police, rescue and firefighting helicopters, for example
• clear of clouds and with surface in sight
• at least 1,500 meters of flight visibility, 800 meters for helicopters
• no more than 140 knots indicated airspeed
• no takeoff or landing clearance below a 600-foot cloud base or below 1,500 meters of ground visibility (helicopters 800 meters)

Visual flight at night

Under SERA, night VFR is only allowed if the competent authority permits it. Then stricter conditions apply: among others a flight plan as soon as the flight leaves the vicinity of the airfield, radio contact where possible, a cloud base of at least 1,500 feet and – unless a minimum altitude is set – clear distance from obstacles: 1,000 feet over flat terrain, 2,000 feet in mountains. The relaxations on flight visibility do not apply at night.

How an instrument flight works

An IFR flight begins long before taxiing. The airline or the pilot files a flight plan. Before takeoff, the crew receives an en route clearance with departure route, initial altitude and transponder code. The flight then follows a chain of set elements:

How departure and arrival routes are built is explained in the guide SID and STAR, and the technology behind the precision approach in the article ILS approach explained.

For altitude there is a simple basic rule: except during takeoff and landing, an IFR flight must keep at least the minimum altitude set by the state overflown. If there is none, 1,000 feet above the highest obstacle within 8 kilometers applies, and over high terrain or in mountains 2,000 feet.

A visual approach is not visual flight

At the spot, you sometimes see an airliner flying a curve straight onto the runway instead of a long, straight final approach. That is often a visual approach. The crew has the airport in sight and may complete the approach without an instrument procedure. The flight nevertheless remains an IFR flight under the control of air traffic control – it does not switch to VFR.

Switching between VFR and IFR

A flight doesn’t have to take place under one rule throughout. In the flight plan, the field for the flight rules specifies what is planned:

• I – the entire flight under IFR
• V – the entire flight under VFR
• Y – takeoff under IFR, later change to VFR
• Z – takeoff under VFR, later change to IFR

Typical for Z is a small aircraft that takes off by sight from an airfield without instrument procedures and only joins the IFR system in the air. Conversely, an IFR flight can be ended en route, for example when the destination is a small airfield without an approach procedure. To do so, the pilot must explicitly tell air traffic control that they are canceling their IFR flight – the prescribed phrase in English radio communication is “cancelling my IFR flight.” Air traffic control may not suggest the change on its own initiative.

The altitude gives away the flight rule

Above 3,000 feet above ground, aircraft in cruise use set altitudes that depend on the course (semicircular cruising levels). The system separates IFR and VFR traffic by the number alone:

Course (magnetic)	IFR cruising levels	VFR cruising levels
000 to 179 degrees (roughly eastbound)	odd thousands, e.g. FL 50, FL 70, FL 90	odd thousands plus 500, e.g. FL 35, FL 55, FL 75
180 to 359 degrees (roughly westbound)	even thousands, e.g. FL 60, FL 80, FL 100	even thousands plus 500, e.g. FL 45, FL 65, FL 85

Air traffic control can assign altitudes that deviate from this, and up to 3,000 feet above ground the scheme doesn’t apply. As a rule of thumb, it still works well: if you see a small aircraft steady at 5,500 feet on your tracking app, it is very likely flying by sight. How to receive such data yourself is explained in the guide Flight tracking with ADS-B for spotters.

There is an upper limit for VFR as well: above flight level 195, visual flights are only allowed in reserved airspace or under special procedures, and above flight level 285 they are not approved where the reduced vertical separation of 1,000 feet applies. Flights at near-sonic or supersonic speed are also prohibited under VFR without authority approval.

What you notice of it as a spotter

On the aviation radio

If you listen to aviation radio, you quickly recognize the two worlds. IFR flights check in with callsign, altitude and clearances for departure or arrival routes, and controllers give headings and altitudes. Visual-flight pilots at a control zone, by contrast, often report at compulsory reporting points at the edge of the CTR, ask for entry or transit and are assigned visual routes. At small airfields without air traffic control, you hear the flight information service or self-announcements in the traffic pattern – often in German, because in visual flight in Germany German is permitted alongside English. More in English or German on aviation radio and Radio phraseology explained. Before you switch on: what applies legally when listening in is summarized in Listening to aviation radio: the legal situation.

On the transponder

The transponder code provides another hint. IFR flights usually get their code with the en route clearance. Aircraft that don’t use an air traffic service generally set 7000 in Europe under SERA – these are almost always visual flights. What the emergency codes mean is in the article Squawk 7500, 7600, 7700, and the technology behind it in Mode S transponders explained.

At the fence and on the apron

At hubs like Frankfurt Airport, IFR traffic dominates almost completely. At airports with significant general traffic like Hamburg Airport, visual-flight aircraft mix into operations on good days, too. And at small airfields, VFR is the normal case: training aircraft like the Cessna 172 fly traffic patterns there, and on weekends with high-pressure weather it gets busy. How to find such airfields is shown by Finding small airfields on maps, and for identifying the aircraft, Recognizing light aircraft helps.

The borderline cases are exciting: a turboprop like the Pilatus PC-12 is equipped for instrument flight and can fly under IFR or VFR depending on the mission. Whether the small aircraft lands in the morning despite low clouds is therefore often already revealed by the type.

VFR day or IFR day? Your spotting decision

What to keep in mind

• VFR doesn’t mean no radio. Visual-flight pilots, too, have radio and transponder requirements depending on the airspace, and in control zones they need a clearance.
• IFR doesn’t mean bad weather. Almost all scheduled traffic always flies IFR, even in the best sunshine.
• Rules can differ nationally. SERA is the common basis in Europe, but authorities can set relaxations and additional rules. For details, the respective aeronautical publication always applies.
• Visibility is not the same as visibility. The weather report gives the ground visibility at the airport. The flight visibility the pilot has in the cockpit can differ.
• Not pilot knowledge for real-world use. This article explains the basics for spotters. Anyone who wants to fly themselves learns the rules fully in training – an overview is in Becoming a pilot: the paths.

Conclusion

Visual flight and instrument flight are two sets of rules for the same sky. VFR relies on sight and personal responsibility and is tied to clear weather limits: as a rule 5 kilometers of visibility, sufficient cloud clearance and, in control zones, a cloud base of at least 1,500 feet. IFR relies on procedures, equipment and air traffic control and works in the clouds too – which is why scheduled traffic practically always flies under it. For you as a spotter, the difference is a practical tool: it explains what you hear on the radio, which flight levels you see on the live map and whether the trip to the small airfield is worth it today.