Dense fog, heavy rain, or a blizzard can blanket an airport, drastically reducing how far pilots can see. In the past, this meant widespread cancellations and delays. Today, airports and airlines use a specific set of rules to keep flying safely, even when the weather doesn't cooperate. These rules are known as Low Visibility Operations.

LVOs are critical for maintaining the flow of air traffic. They allow airports to continue operating, preventing the ripple effect of delays that can disrupt travel for thousands of people. But this efficiency never comes at the cost of safety. LVOs are built on strict, internationally agreed-upon standards that ensure every movement on the ground and in the air is carefully managed.

But what exactly qualifies as "low visibility"? It's not just a pilot looking out the window and making a judgment call. Aviation authorities use a precise measurement called Runway Visual Range.

RVR is measured by instruments called transmissometers placed alongside the runway. They provide pilots and air traffic controllers with real-time, objective data about the visibility exactly where it matters most: on the runway itself. This measurement is typically given in feet or meters.

When the RVR drops below a specific value, an airport doesn't just operate as usual. It formally declares that it's implementing Low Visibility Procedures (LVPs). Think of LVPs as the official rulebook for bad weather operations.

Once LVPs are in effect, everything on the airfield moves with greater caution. The number of aircraft allowed to taxi or be near the runway is reduced to prevent collisions. This is why, even with LVOs, you might experience some delays. Safety requires giving each aircraft more space and time.

These procedures cover both departures and arrivals. A takeoff performed under these conditions is called a Low Visibility Take-Off (LVTO). For an LVTO to be permitted, the RVR must be above a certain minimum, which can be as low as 75 meters (about 250 feet) for specially certified aircraft and crews. For landings, the minimum RVR depends on the type of approach being flown and the equipment on the aircraft and at the airport. LVPs remain active until the visibility improves and stays consistently above the required RVR value.

During a low visibility approach, every pilot has a critical altitude in mind known as the Decision Height. This is the point of no return.

When the aircraft reaches the Decision Height, the pilot must have the required visual references in sight, like the runway approach lights. If they can't see them, they are required to abort the landing and fly a "go-around." This is not an emergency; it's a standard safety procedure that ensures a landing is only attempted when it is safe to do so. The specific DH for an approach is published on aeronautical charts and can be as low as just a few hundred feet above the ground.

Ultimately, LVOs are a carefully balanced system. They combine advanced technology, strict regulations, and rigorous training to ensure that air travel can continue safely and efficiently, no matter what the weather looks like outside.