Fog is one of the most dramatic things a passenger can experience on a flight: the world outside disappears, and yet the plane lands smoothly on the runway. It feels like a leap of faith, but it is the opposite. Landing in fog is one of the most rehearsed, rule-bound procedures in aviation, built on instruments, training, and strict limits that everyone follows.

The key idea is that pilots in fog are not flying by sight at all. They are flying by instruments that tell them exactly where the plane is relative to the runway, and they follow procedures that define, to the metre, how low they may go before they must either see the runway or abandon the landing.

A precision approach uses ground-based or satellite guidance to give the pilots a precise path down to the runway: the correct lateral line and the correct descent angle. The pilots monitor these instruments constantly, cross-checking them against each other and against the aircraft's speed and altitude, while air traffic control keeps other traffic clear.

The approach has a decision point, a minimum height below which the pilots must see specific runway references, such as the lights or markings, or go around. This is not a judgement call made in the moment. It is a number briefed before the approach begins, and if the references are not visible at that height, the pilots climb away and try again or divert. No exceptions, no peering.

In very low visibility, the aircraft may fly the landing automatically. Autoland systems can guide the plane all the way to touchdown and even along the runway, using precision signals and redundant systems that cross-check each other. Pilots monitor the system throughout and are trained to take over instantly if anything disagrees.

Autoland requires special airport equipment, specially trained crews, and specific aircraft certification, which is why not every airport and aircraft can do it. When any piece is missing, the visibility limits are higher, and flights may be delayed or diverted instead. That caution is the system working, not failing.

If fog landing is so capable, why do flights still delay? Because capacity drops. Low-visibility procedures require greater spacing between aircraft, fewer runways in use, and slower ground movement, since planes and vehicles on the ground also cannot see each other well. An airport that handles dozens of landings an hour in clear weather may handle a fraction of that in thick fog.

So a fog delay usually means the airport is being careful, not that landing is impossible. The pilots, the instruments, and the procedures can handle far worse visibility than passengers imagine. What they cannot do is handle it quickly, and that slower pace is the price of landing safely when you cannot see the runway until the last seconds.

When fog delays your flight, the most useful thing you can do is stay informed and flexible. Check the airline's app for rebooking options before joining a long queue, and consider whether an alternative route or a later flight serves you better than waiting for your original departure. Airlines rebook in order, and early action gives you more choices.

Use the waiting time practically: confirm hotel or meeting arrangements at your destination, keep your phone charged, and keep essentials accessible rather than buried in checked luggage. Fog delays are frustrating precisely because they are nobody's fault, but passengers who treat them as a logistics problem to solve, rather than an injustice to endure, usually reach their destination with less stress.