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During the day, pilots approaching an airport use dozens of visual cues to judge altitude and distance: the size of buildings, the texture of fields, the movement of terrain in their peripheral vision, and the contrast between the runway surface and its surroundings. At night, most of those cues disappear. Over unlit terrain or water, the only visible references may be the runway lights themselves, floating in darkness with no surrounding context. The brain interprets the geometry of those lights as if the aircraft is higher than it actually is, producing a tendency to fly below the correct glidepath. The FAA calls this the black hole effect, and it has caused controlled flight into terrain accidents at airports where the approach crosses featureless ground or water on dark nights.
The illusion is not limited to the black hole. City lights climbing hillsides can create false horizons. Mountains that are prominent landmarks during the day become invisible obstacles at night. Competing light sources at different elevations confuse the brain’s attempt to construct a coherent picture of where the ground is relative to the aircraft. These five airports each produce a different version of the same problem: a night approach where the visual picture either provides no useful information or actively misleads the crew into perceiving something that is not there.
Daniel K. Inouye International Airport
Over the open Pacific on a moonless night
Red-eye flights from the US mainland to Daniel K. Inouye International Airport (HNL) arrive before dawn after crossing 2,400-2,600 nautical miles (4,445-4,815 km) of open Pacific. For the final several hundred miles, nothing lies below the aircraft but water. No ground lights, no terrain features, no roads. On a moonless night with overcast skies, the ocean and the sky merge into a featureless void. The visual cues that help a pilot judge altitude, distance, and glidepath during a daytime approach are absent entirely.
HNL operates four runways on Oahu’s south shore, including the reef runway built on a coral reef offshore. Depending on the active configuration, approaches may cross open water, Ke’ehi Lagoon, or the suburban coastline west of the airport. Approaches that cross water on a dark night produce classic black hole conditions: the pilot sees the runway lights ahead but has no peripheral references below or beside the aircraft to confirm altitude. Without those cues, the brain interprets the runway light geometry as if the aircraft is higher than it actually is, producing a tendency to fly below the correct glidepath.
Commercial crews flying overnight sectors into HNL brief the overwater black hole risk as a standard approach briefing item. Airline procedures for overnight arrivals typically require flying the ILS to decision altitude rather than transitioning to a visual approach early. The ILS provides continuous glideslope and localizer guidance that keeps the crew on the correct path regardless of what the outside visual picture suggests. The PAPI at each runway threshold provides additional glidepath confirmation, but on a dark night with no peripheral references, the instrument approach is the primary defense against the illusion that has caused CFIT accidents at overwater airports worldwide.
Nice Côte d’Azur Airport
City lights that create a false horizon
Nice-Côte d’Azur Airport (NCE) sits on reclaimed land on the Mediterranean coast with Runways 04L and 04R facing northeast over the sea. Approaches from the southwest cross several miles of featureless Mediterranean water before reaching the threshold. During the day, the Promenade des Anglais and Nice’s densely built hillsides provide abundant visual references. At night, the water is black and the visual references are replaced by the lights of the Côte d’Azur climbing steeply into the foothills of the Alpes-Maritimes behind the airport.
Those hillside lights create a false horizon. The city of Nice rises sharply from the coast, with residential and commercial lighting extending hundreds of meters above sea level. A pilot on approach at night can unconsciously interpret the band of hillside lights as the horizon when the actual horizon is the invisible boundary between the dark sea surface and the sky above it. If the pilot aligns the approach angle with the perceived horizon rather than the real one, the approach appears steeper than it is, which can lead to descending below the correct glidepath without recognizing the error.
The combination of overwater black hole conditions on the approach path and a false horizon behind the runway makes NCE a textbook case of competing night visual illusions. Crews flying the ILS to Runways 04L or 04R use the glideslope and PAPI as primary references rather than transitioning to visual references early. Airline operating procedures for NCE typically require instrument approaches at night regardless of how clear the visibility appears, because the visual picture at NCE on a dark night is precisely the kind that produces confident but incorrect altitude perception.
Cristiano Ronaldo International Airport
A cliffside runway over the Atlantic
Cristiano Ronaldo International Airport (FNC) on the island of Madeira is classified as a Category C facility by the Portuguese aviation authority, meaning it poses specific challenges during approach, landing, and takeoff. The runway sits on a narrow plateau on the island’s east coast, with a significant portion built on a platform supported by 180 pillars rising 230 feet (70 meters) above the Atlantic coastline below. Terrain rises rapidly to the northwest, reaching 2,500 feet within three nautical miles (5.6 km) and 6,110 feet at the island’s highest peak within nine nautical miles (16.7 km). The approach to Runway 05 requires a curved visual maneuver around the terrain. Runway 23 uses an offset final approach course for the same reason.
Catch what other flight trackers miss
Emergency squawks, holds, NOTAMs — live signals, no signup.
Open tracker
Catch what other flight trackers miss
Emergency squawks, holds, NOTAMs — live signals, no signup.
Open tracker
Night operations at Funchal are permitted, but the Portuguese AIP requires that any captain operating at the airport after dark must have previous experience at the airport in daylight. All approaches in both runway directions are ultimately performed visually, regardless of weather conditions. Captains must have a minimum of 200 flying hours on type and must have completed at least one takeoff and landing at Funchal within the previous six months, or have completed approved simulator training. Airlines wishing to fly into Funchal require specific approval from the Portuguese aviation authority.
At night, the mountains surrounding the airport on three sides are invisible. The Atlantic below the runway platform is featureless. The curved approach to Runway 05, which requires the pilot to fly a visual arc around high terrain before aligning with the runway, becomes much more demanding when the pilot cannot see the terrain they are avoiding. The combination of invisible obstacles, overwater final approach segments, and a runway perched on pillars above the ocean makes Funchal one of the airports where the gap between a daytime visual approach and a nighttime one is widest.
Juneau International Airport
Mountains, water, and no visual approaches after dark
Juneau International Airport (JNU) sits in a narrow valley on the Alaska Panhandle, flanked by mountains rising to 3,500-4,000 feet on multiple sides. The Gastineau Channel runs along the airport’s southern boundary. During the day, the mountains are visible and the pilot can navigate the valley visually, maintaining clearance from the ridgelines that constrain the approach path. At night, the mountains disappear. The rock faces, tree lines, and ridgelines that define the valley’s boundaries become invisible against a dark sky. The channel below is featureless water.
Night approaches at Juneau rely on instrument procedures that navigate the aircraft through the valley using altitude restrictions and course guidance designed to keep it clear of surrounding terrain. The LOC approach to Runway 08 uses step-down fixes to lower the aircraft in stages between the mountains. Missed approach procedures route the aircraft away from terrain rather than climbing directly overhead. Crews operating into Juneau at night must be familiar with the terrain environment and the specific instrument procedures, because the visual references that make the airport manageable during the day are completely absent after dark.
The challenge at Juneau is not just the absence of visual references but the proximity of the terrain the pilot cannot see. A pilot at Nice or Honolulu who flies slightly below the correct glidepath at night is descending toward water, which provides some margin before impact with rising terrain. A pilot at Juneau who deviates from the instrument procedure at night is potentially descending toward a mountainside less than a mile from the runway centerline. Instrument guidance is not optional at Juneau after dark. It is the only thing between the aircraft and the terrain the crew cannot see.
Santos Dumont Airport
Over the bay between the mountains
Santos Dumont Airport (SDU) occupies a narrow strip of reclaimed land on the western shore of Guanabara Bay in central Rio de Janeiro. Sugarloaf Mountain rises 1,299 feet (396 meters) directly adjacent to the approach path. Corcovado, the peak holding the Christ the Redeemer statue, stands 2,329 feet (710 meters) southwest. Additional peaks and ridgelines surround the bay on multiple sides. During the day, these landmarks are unmistakable visual references that help pilots navigate the approach through the surrounding terrain. At night, granite peaks become invisible silhouettes against a dark sky, identifiable only by the absence of stars where rock blocks the view.
Approaches to SDU cross Guanabara Bay, which is featureless water at night, before threading between Sugarloaf and the urban hillsides to reach the runway. City lights at varying elevations on the hillsides surrounding the bay create multiple competing visual references. Lights on Niterói across the bay, lights climbing the favelas on the hillsides above Botafogo, and lights along the coastal road all sit at different altitudes and distances. A pilot scanning for the runway on a dark approach sees dozens of light sources at different heights with no natural horizon to anchor them. The brain tries to construct a coherent picture from these scattered references, and the result can be a perceived horizon that doesn’t match the actual one.
SDU primarily handles domestic shuttle traffic between Rio and São Paulo, with most flights operated by turboprops and narrowbodies. Operations are restricted to aircraft with 50 seats or fewer on most routes, except the São Paulo shuttle. The airport’s central location in Rio, surrounded by iconic terrain features that become hazards after dark, makes it one of the most visually demanding urban airport approaches in the world after sunset.
