Why towers blink — FAA lighting and marking rules

The whole reason antenna structures are registered with the FCC is aviation. The registration requirement exists so that tall objects can be catalogued, evaluated and — where necessary — made visible to pilots. Everything else the data is useful for is a by-product.

That makes lighting and marking worth understanding, because it is the point of the exercise.

When it applies

The general threshold is 200 feet above ground level. Above that, a structure normally requires obstruction marking and lighting. Below it, generally not — unless the structure is near an airport, where the requirement extends to much shorter objects on a sliding scale with distance from the runway.

The governing document is FAA Advisory Circular 70/7460-1, which specifies the available lighting and marking systems. An FAA aeronautical study determines which system a given structure must use, and the FCC registration records the outcome.

The three approaches

Paint

Alternating bands of aviation orange and white, with an odd number of bands, the top and bottom always orange. Band widths are specified relative to the structure’s height.

Paint alone works only in daylight and only in good visibility, so it is almost always paired with lighting.

Red lights

Steady-burning red at intermediate levels, flashing red at the top. This is the traditional night-time system and remains the most common.

Red lighting is unobtrusive from the ground and effective for pilots at night. Its weakness is daytime, which is why red-lit towers are usually painted as well.

White strobes

High-intensity flashing white, day and night, at a rate around 40 flashes per minute — brighter and faster during the day, dimmer at night.

The advantage is that strobes remove the need for paint, which matters for very tall structures where repainting is a major operation. The disadvantage is that white strobes are extremely visible from the ground, and they are a recurring source of complaints from anyone living within a few kilometres.

Many structures use a dual system: white strobes by day, red by night.

What the pattern tells you

From the ground, at a distance:

• Painted orange and white, red lights at night → over 200 feet, conventional system
• Bright white flashes, day and night, unpainted → over 200 feet, usually well over; often a broadcast mast
• No lighting or marking at all → under 200 feet and away from an airport, which also means it probably is not in the federal register

That last one is the useful inference. If you can see a mast and it has no obstruction lighting, it is likely below the registration threshold and you will not find it in this data. This is the same gap covered here, seen from the other direction.

Migratory birds

Steady-burning red lights attract night-migrating birds, which can circle a lit structure until exhausted. Research through the 2000s and 2010s established the effect and identified flashing lights as substantially less harmful than steady ones.

The FAA subsequently revised its guidance to reduce reliance on steady-burning lights, and many existing structures have been converted. This is one of the clearer cases of an aviation safety rule being changed on ecological evidence, and it has measurably reduced bird mortality at tall structures.

Maintenance and outages

Operators are required to monitor obstruction lighting and to report failures. An outage that cannot be repaired promptly triggers a Notice to Air Missions so that pilots are warned.

If you notice an unlit tall structure at night, that is a genuine safety matter and the FAA and FCC both accept reports. The registration number — which is displayed at the base of registered structures, and on every structure page on this site — is what they will ask for.