Can Planes Fly In Fog? | What Pilots See And Do

Yes, airliners can take off and land in fog when visibility reports and certified equipment meet the runway’s published minimums.

Fog looks like a wall from the terminal. From the flight deck, it’s a numbers-and-systems problem: can the crew stay inside the limits for that runway, right now? Jets can cruise with no view outside, yet takeoff, landing, and taxi still depend on what can safely replace eyesight near the ground.

This article explains what fog does to runway visibility, how airports measure it, what “CAT I/II/III” means, and why one airport keeps landing while another shuts down.

What Fog Changes For A Flight

Fog is tiny water droplets near the surface. It reduces contrast and hides depth cues, so the runway can disappear until the last moments. Close to the ground, pilots must either see the required runway cues or use an approved system that can guide the aircraft to touchdown and keep it aligned after landing.

Two visibility terms show up in airline decisions:

• Prevailing visibility: a broad estimate for the airport area.
• Runway Visual Range (RVR): a sensor-based value for how much runway lighting or markings a pilot can see from the runway centerline.

Fog can be patchy. One end of the runway may report a higher RVR than the other, so controllers may report “touchdown,” “mid,” and “rollout” values. Those numbers drive what approaches are allowed.

Why Takeoff And Landing Get Different Rules

Takeoff is often less restrictive than landing in fog. On takeoff, the aircraft accelerates on a known surface with straight-line cues and can reject the takeoff early if needed. On landing, the aircraft is descending and slowing while trying to line up with the runway. If the runway cues aren’t visible by a set point, the crew must go around.

That set point is published on the approach as a decision height (DH) or minimum descent altitude (MDA). It’s the moment the crew must have the required visual references or start the missed approach.

Can Planes Fly In Fog? What Actually Limits The Flight

The aircraft’s ability to stay airborne is rarely the limit. The limit is whether the runway system, the crew, and the aircraft are authorized for the reported visibility on that runway. Airlines don’t “take a chance” because the rules are built around repeatable cues: if the reported RVR is below the published minimum, the approach can’t continue to landing.

Airports also use low-visibility surface plans. When RVR drops far enough, controllers slow taxi flows, increase spacing, and protect sensitive areas around ILS antennas so signals stay clean. The FAA notes that airports may use low visibility taxi plans for operations in less than 1,200 feet RVR. FAA Aeronautical Information Manual section on airport operations describes how these plans can add lighting, markings, and procedures to control movement on the airfield.

What “CAT I, CAT II, CAT III” Means

“CAT” labels describe how low the visibility and ceiling can be for a precision approach, based on runway equipment and airline authorization.

• CAT I: common at many airports; higher minimums.
• CAT II: lower minimums; needs extra lighting, monitoring, and approvals.
• CAT III: the lowest minimums used in airline service; often paired with autoland and stronger redundancy.

Not each runway with an ILS is certified for CAT II or CAT III. Even at big hubs, one runway may carry the low-visibility load while others revert to higher minimums.

What Counts As “Runway In Sight”

Pilots aren’t looking for a vague glow. Procedures list the visual references that count at the decision point. Depending on the runway and category, that can include:

• Approach light system
• Runway threshold lights or markings
• Runway edge lights
• Touchdown zone lights
• Runway centerline lights

If the required cues are not identifiable and stable, the missed approach is the call. That rule also protects against a brief “peek” through thin fog that vanishes again seconds later.

How Airports Measure Visibility In Fog

RVR comes from sensors placed along the runway, often near the touchdown zone, midfield, and rollout end. They estimate how far runway lights can be seen along the runway axis. Controllers pass those values to pilots and they appear in weather reports when conditions call for it.

In the U.S., RVR equipment and reporting follow FAA standards used for weather reporting and operational decisions. FAA Order 6560.10D on Runway Visual Range defines terms and reporting concepts used in the system.

Why Fog Cancels Flights Even When Some Planes Land

• Runway mismatch: arrivals may be using the one runway certified for lower minimums while other runways pause.
• Equipment status: an inoperative RVR sensor, lighting issue, or ILS status change can raise minimums fast.
• Traffic flow: low visibility means more spacing and slower taxi, so the airport handles fewer flights per hour.

Dispatch also plans for fog before the wheels leave the gate. If forecasts are close to minimums, airlines carry extra fuel for a hold, a go-around, and a diversion, plus the required reserves. When alternates nearby are also foggy, dispatch may select a farther alternate, which can force payload limits or longer delays while fuel is uploaded.

Flying In Fog On Airlines: The Rules That Decide Go Or No-Go

Airline dispatch and the flight crew check a short list before committing to an approach in fog: the runway’s published minimums, the latest RVR reports, crosswind limits for that approach category, and whether the aircraft is dispatched with the required systems working. If any piece isn’t there, the plan changes to a higher-minimum runway, a hold for improvement, or a diversion.

In the cockpit, the approach is flown the same way whether the view outside is clear or blank: track the lateral and vertical guidance, verify the right modes are engaged, and stay ready for a missed approach. The outside cues are expected to appear late in fog. The decision is made at DH/MDA based on the required references, not a gut feeling.

Approach Levels And What They Enable

Minimums vary by runway, aircraft, airline approval, and local procedure. The table below shows the practical differences you’ll hear about in airline operations.

Level	What Must Be In Place	What It Lets The Crew Do
Visual approach	Runway visible early	Land using outside cues
CAT I ILS	Standard ILS and approach lighting	Continue to published DH with higher RVR
CAT II ILS	Extra runway lighting and approvals	Continue to a lower DH with lower RVR
CAT IIIA ILS	Autoland-capable aircraft and runway centerline lighting	Land with limited outside cues late in the flare
CAT IIIB ILS	Autoland with rollout guidance and tighter surface controls	Land and track the centerline with minimal outside view
Low-visibility takeoff	Approved takeoff minima and centerline cues	Depart when RVR is low but above the operator’s limit
Low-visibility taxi procedures	Stop bars, centerline lights, routing control	Move aircraft and vehicles with reduced conflict risk
Missed approach	Published climb and navigation path	Go around safely when visual cues aren’t acquired

What Autoland Changes And What It Doesn’t

Autoland can guide the airplane to touchdown using ILS signals and onboard computers, yet it’s still a monitored operation. Crews cross-check mode annunciations, watch for signal issues, and stay ready to go around. A small system fault that is fine in clear weather can block CAT III because redundancy margins are tighter when visibility is low.

Why Some Airports Handle Fog Better

Fog performance is tied to infrastructure. Airports that invest in low-visibility capability usually have:

• Better runway lighting: centerline and touchdown zone lighting help after landing.
• Higher-category ILS certification: tighter tolerances and continuous monitoring.
• Surface movement controls: stop bars, ground surveillance, and defined taxi routes.

Layout matters too. Closely spaced parallel runways may lose capacity in low visibility because aircraft need more separation for safety.

What Delays Look Like When Fog Hits

Fog delays are rarely a single cause. They stack: arrival spacing grows, taxi slows, gate availability tightens, and crews run into duty limits. The table below translates common passenger-facing messages into what is usually happening behind the scenes.

Passenger Message	What It Often Means	What You Can Do
“Awaiting release time”	Air traffic flow management is metering departures	Check connection options early
“Holding for weather at destination”	RVR or ceiling is near or below minimums	Watch nearby alternate airports too
“Taxi delay”	Low-visibility taxi procedures are active	Expect slow movement and longer queues
“Waiting for a gate”	Arrivals are backed up and gates aren’t clearing	Plan for missed connections on tight turns
“Diverting”	Conditions dropped below minima or equipment status changed	Ask the airline about refuel and re-dispatch plans
“Crew issue”	Delays pushed the crew near duty limits	Rebook sooner rather than later
“Canceling for schedule reset”	Aircraft rotations broke and spare planes are limited	Try alternate airports or airlines

Practical Tips For Fog-Prone Travel Days

A few choices can reduce the odds that fog wrecks your day:

• Prefer airports with strong low-visibility capability: large hubs often keep at least one runway open longer.
• Give yourself connection time: low visibility slows both air and ground movement.
• Lean toward mid-day when you have flexibility: fog often lifts after sunrise, though it can linger.
• Track your inbound aircraft: if it’s late leaving the origin, your delay is already baked in.

Safety Notes That Matter

Fog operations rely on layers: runway lighting, RVR sensors, precision approach guidance, onboard redundancy, and strict procedures. If any layer drops out, the minimums rise or the operation stops. That’s why fog produces delays far more often than it produces incidents.

So yes, planes can fly in fog. The better question is whether the whole system is approved for the visibility that exists right now, on that runway, with that aircraft and crew. When the answer is no, the safest outcome is a delay, a go-around, or a diversion.