Anticipatory anxiety of being out of control and overwhelmed can prevent a person from planning to travel by air. The thought of an upcoming flight can cause great distress, particularly when compelled to travel by air. The most extreme manifestations can include panic attacks or vomiting at the mere sight or mention of an aircraft or air travel.

Acrophobia (from the , "ákron", meaning "peak, summit, edge" and , "phóbos", "fear") is an extreme or irrational fear or phobia of heights, especially when one is not particularly high up. It belongs to a category of specific phobias, called space and motion discomfort, that share both similar causes and options for treatment.

Most people experience a degree of natural fear when exposed to heights, known as the fear of falling. On the other hand, those who have little fear of such exposure are said to have a head for heights. A head for heights is advantageous for those hiking or climbing in mountainous terrain and also in certain jobs e.g. steeplejacks or wind turbine mechanics.

Acrophobia sufferers can experience a panic attack in high places and become too agitated to get themselves down safely. Approximately 2–5% of the general population suffers from acrophobia, with twice as many women affected as men.

Fear of flying is a fear of being on an airplane (aeroplane), or other flying vehicle, such as a helicopter, while in flight. It is also referred to as flying phobia, flight phobia, aviophobia or aerophobia (although the last also means a fear of drafts or of fresh air).

Fear of flying may be a distinct phobia in itself, or it may be an indirect combination of one or more other disorders, such as claustrophobia (a phobia of being restricted, confined, or unable to escape) or acrophobia (anxiety or dread of being at a great height). It may have other causes as well, such as agoraphobia (especially the type associated with having a panic attack in a place they can't escape from). It is a symptom rather than a disease, and different causes may bring it about in different individuals.

This phobia receives more attention than most other phobias because air travel is often difficult for people to avoid—especially in professional contexts—and because it is common, affecting a significant minority of the population. Inability to maintain emotional control when aloft may prevent a person from going on vacations or visiting family and friends, and it can cripple the career of a businessperson by preventing them from traveling on work-related business.

Traditionally, acrophobia has been attributed, like other phobias, to conditioning or a traumatic experience. Recent studies have cast doubt on this explanation; a fear of falling, along with a fear of loud noises, is one of the most commonly suggested inborn or "non-associative" fears. The newer non-association theory is that a fear of heights is an evolved adaptation to a world where falls posed a significant danger. The degree of fear varies and the term phobia is reserved for those at the extreme end of the spectrum. Researchers have argued that a fear of heights is an instinct found in many mammals, including domestic animals and humans. Experiments using visual cliffs have shown human infants and toddlers, as well as other animals of various ages, to be reluctant in venturing onto a glass floor with a view of a few meters of apparent fall-space below it. While an innate cautiousness around heights is helpful for survival, an extreme fear can interfere with the activities of everyday life, such as standing on a ladder or chair, or even walking up a flight of stairs.

A possible contributing factor is a dysfunction in maintaining balance. In this case the anxiety is both well founded and secondary. The human balance system integrates proprioceptive, vestibular and nearby visual cues to reckon position and motion. As height increases, visual cues recede and balance becomes poorer even in normal people. However, most people respond by shifting to more reliance on the proprioceptive and vestibular branches of the equilibrium system.

An acrophobic, however, continues to over-rely on visual signals whether because of inadequate vestibular function or incorrect strategy. Locomotion at a high elevation requires more than normal visual processing. The visual cortex becomes overloaded resulting in confusion. Some proponents of the alternative view of acrophobia warn that it may be ill-advised to encourage acrophobics to expose themselves to height without first resolving the vestibular issues. Research is underway at several clinics.

Gephyrophobia is the anxiety disorder or specific phobia characterized by the fear of bridges. As a result, sufferers of gephyrophobia may avoid routes that will take them over bridges.

Some possible explanations of gephyrophobia may be the fear of driving off the bridge, the fear of a gust of wind taking one off the bridge, a fear of the structural integrity of the bridges itself, or the fear that the bridge will collapse if they try to cross it. The fear overlaps with acrophobia, the fear of heights, as gephyrophobia tends to be exacerbated in tall bridges vs. ones close to the water/ground beneath.

Dr. Michael Liebowitz, founder of the Anxiety Disorders Clinic at the New York State Psychiatric Institute, says, "It's not an isolated phobia, but usually part of a larger constellation ... It's people who get panic attacks. You get light-headed, dizzy; your heart races. You become afraid that you'll feel trapped." It is a situational phobia.

The New York State Thruway Authority will lead gephyrophobiacs over the Tappan Zee Bridge. A driver can call the authority in advance and arrange for someone to drive the car over the bridge for them. The authority performs the service about six times a year.

The Maryland Transportation Authority offers a similar service for crossing the Chesapeake Bay Bridge.

The Mackinac Bridge Authority, which oversees the Mackinac Bridge, which connects Michigan’s Upper and Lower peninsulas, will drive one's car across its span for any needy gephyrophobiacs. Some thousand drivers take advantage of this free program each year. Leslie Ann Pluhar had her Yugo blown off that bridge. Later investigation showed the driver had stopped her car over the open steel grating on the bridge's span and that a gust of wind through the grating blew her vehicle off the bridge, although this is not supported by recorded wind speed measurements taken on and around the bridge at the time of the accident.

The term "gephyrophobia" comes from Greek γέφυρα ("gephura") meaning "bridge" and φόβος ("phobos") "fear".

Most phobias are classified into three categories and, according to the "Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition" (DSM-V), such phobias are considered to be sub-types of anxiety disorder. The categories are:

1. Specific phobias: Fear of particular objects or social situations that immediately results in anxiety and can sometimes lead to panic attacks. Specific phobia may be further subdivided into five categories: animal type, natural environment type, situational type, blood-injection-injury type, and other.

2. Agoraphobia: a generalized fear of leaving home or a small familiar 'safe' area, and of possible panic attacks that might follow. It may also be caused by various specific phobias such as fear of open spaces, social embarrassment (social agoraphobia), fear of contamination (fear of germs, possibly complicated by obsessive-compulsive disorder) or PTSD (post traumatic stress disorder) related to a trauma that occurred out of doors.

3. Social phobia, also known as social anxiety disorder, is when the situation is feared as the person is worried about others judging them.

Phobias vary in severity among individuals. Some individuals can simply avoid the subject of their fear and suffer relatively mild anxiety over that fear. Others suffer full-fledged panic attacks with all the associated disabling symptoms. Most individuals understand that they are suffering from an irrational fear, but are powerless to override their panic reaction. These individuals often report dizziness, loss of bladder or bowel control, tachypnea, feelings of pain, and shortness of breath.

The fear of falling (FOF), also referred to as basophobia (or basiphobia), is a natural fear and is typical of most humans and mammals, in varying degrees of extremity. It differs from acrophobia (the fear of heights), although the two fears are closely related. The fear of falling encompasses the anxieties accompanying the sensation and the possibly dangerous effects of falling, as opposed to the heights themselves. Those who have little fear of falling may be said to have a head for heights. Basophobia is sometimes associated with astasia-abasia, the fear of walking/standing erect.

A specific phobia is any kind of anxiety disorder that amounts to an unreasonable or irrational fear related to exposure to specific objects or situations. As a result, the affected person tends to avoid contact with the objects or situations and, in severe cases, any mention or depiction of them. The fear can, in fact, be disabling to their daily lives.

The fear or anxiety may be triggered both by the presence and the anticipation of the specific object or situation. A person who encounters that of which they are phobic will often show signs of fear or express discomfort. In some cases, it can result in a panic attack. In most adults, the person may logically know the fear is unreasonable but still find it difficult to control the anxiety. Thus, this condition may significantly impair the person's functioning and even physical health.

Specific phobia affects up to 12% of people at some point in their life.

Unlike specific phobias, social phobias include fear of public situations and scrutiny, which leads to embarrassment or humiliation in the diagnostic criteria.

Studies done by psychologists Eleanor J. Gibson and Richard D. Walk have further explained the nature of this fear. One of their more famous studies is the "visual cliff. Below is their description of the cliff:

Thirty-six infants were tested in their experiments, ranging from six to fourteen months. Gibson and Walk found that when placed on the board, 27 of the infants would crawl on the shallow side when called by their mothers; only three ventured off the "edge" of the cliff. Many infants would crawl away from their mothers who were calling from the deep end, and some would cry because they couldn’t reach their mothers without crossing an apparent chasm. Some would pat the glass on the deep end, but even with this assurance would not crawl on the glass. These results, although unable to prove that this fear is innate, indicate that most human infants have well developed depth perception and are able to make the connection between depth and the danger that accompanies falling.

According to the fourth revision of the "Diagnostic and Statistical Manual of Mental Disorders", phobias can be classified under the following general categories:

- Animal type – Fear of dogs, cats, rats and/or mice, pigs, cows, birds, spiders, or snakes.

- Natural environment type – Fear of water (aquaphobia), heights (acrophobia), lightning and thunderstorms (astraphobia), or aging (gerascophobia).

- Situational type – Fear of small confined spaces (claustrophobia), or the dark (nyctophobia).

- Blood/injection/injury type – this includes fear of medical procedures, including needles and injections (trypanophobia), fear of blood (hemophobia) and fear of getting injured.

- Other – children's fears of loud sounds or costumed characters.

Gephyrophobia is the name of a map in the video game ""; the two bases are connected only by a bridge flanked by snipers' outposts. The name most likely comes from the fact that the players are frequently killed on the bridge.