¶ … Aviation Fatigue has been recognized as a causal factor in accidents, injuries and death in a vast range of situations, which indicate that tired people have a lessened likelihood and probability to give sound performance of a safe action. The situational areas can include industries like transport such as road, air, rail and oceanic as well as occupational areas such as; hospitals, emergency operations, law enforcement etc. And the problem is more particular in the working hours that are irregular. Almost everyone is caught complaining of fatigue at some point of time, either on work or leisure time, and that ultimately causes accidents and injuries. Fatigue causes slow responses and failure to pay attention or inappropriate action which can be the primary causes leading to most of the accidents (Mitler et al., 1988).

In most of the countries, fatigue is understood to be the most prominent accident factor in the aviation industry (Horne and Reyner, 1995a; Lyznicki et al., 1998; Pierce, 1999; Philip et al., 2001; Dobbie, 2002). The estimation of its role can vary because of the different circumstances and severity of the accidents. Normal range which is estimated is in between 1% to 3% of all accidents (Lyznicki et al., 1998) to 20% of accidents on the motorways (Horne and Reyner, 1995b).

It is a general perception that any kind of percentage based on accidents does not depict the real magnitude of the dilemma; hence the involvement of fatigue cannot be questioned in the accident because it excludes other factors, which may contribute to the accident.

The fundamental objective of the paper is to provide the scientific evidence of the relationship between safety and fatigue and will analyze the following questions:

Is there any link between the fatigue and safety?

Are there evidences to be concerned about the causes of fatigue?

What are the gaps in the knowledge?

Whatever may be the understanding of the fatigue and its impact, the issue does not get a clear and defined meaning and context of fatigue. It is a hypothetical statement which is contingent because it produces the calculable phenomena which cannot be measured objectively. Fatigue can be linked a lot of factors which cause it and hence one can come up with a number of safety related outcomes. The long period without sleep and accidents are among the projected effects of fatigue.

There is dispute on the definition of fatigue as mentioned before (Desmond and Hancock, 2001; Noy et al., 2011). In this review, we will define it as 'biological drive for restorative rest'. This rest can and cannot involve a period of time, and depends upon the framework of the fatigue. There are lots of types of fatigue such as mental sleepiness or physical/muscular one. Everything here depends upon the causes and its nature.

With regards to the modern transportation system, it is more evident that mental fatigue and sleepiness are the basic and important forms of fatigue. For this study, our focus will revolve around all kinds of fatigue which can result in lowered performance and safety issues or incorrect responses or complete failure in responding (Williamson et al., 2011).

Literature review and hypotheses

According to Karasek's job strain model in 1979, the psychological damage that occurs upon a human being is usually because of the intense aviation workload one has to deal with and the amount of time that one has to spend on it. Furthermore, Karasek's (1979) explains that the major reason for psychological pressure is that every job requires a lot of energy and concentration and it is usually too much for one to manage. Obviously it becomes very difficult for the employees in aviation to manage their resources properly if the amount of work outweighs the resources available to them. These types of work conditions have a negative impact on the performance of the employee (Karasek, 1979)

The major point of Karasek's study was that exaggerated amounts of work do have a damaging affect on the employee in aviation. The study on the other hand does not investigate whether events through which stress increases actually increase the demand for the job because of which employees in aviation willfully have to cut down on their leisure and relaxation time. According to Elavainio and Kivima (1996) when employees are aware of all the processes of their work and are thoroughly involved in the work, there is a lower chance of stress. Taking this one step ahead, it becomes easier for the employee to manage stress when his or her role is defined clearly (Bliese...

But again the study does not cover every aspect because there is no mention of how role uncertainty, role divergence and high workload really impact the level of stress in employees. This is why we are trying to study how these three things can affect the stress level.
While this study is definitely focused on the impact stress factors play on employees in aviation, we will also discuss the role of working in shifts and having control over processes in relation to how much more stress is put on the employee and figure out the connection between stress and how it affects the employee performance. Van Vegchel (et al., 2005) and Totterdell (et al., 2006) tell us that we need to work with a two-way communication approach (which is also the Demand-Control [DQ] model), which is more effective than the additive approach.

In this study we are going to figure out how job control with relation to a particular work in aviation affects job demand. This is the reason why our focus will now turn towards shift work and how it affects the demand of a job on the employee. Another way to lessen the strain on the employees regarding their work demand is to delegate work and give more freedom to express their viewpoints. This definitely affects the level of stress.

Shift work in aviation

The main focus of this part of the study will be shift work. We will try to acquire knowledge about how the fixed or rotating shifts impact the level of stress on the employees in aviation and whether employees reporting high levels of stress work in fixed, or in rotating shifts.

Undoubtedly, more risk is undertaken by those individuals who are deprived of sleep since they bypass their rational calculation (Harrison and Horne, 2000), and the psychomotor vigilance task displays low response speed (Petrilli et al., 2006). Moreover, as stated by Folkard et al. (1990), low alertness, fatigue, ad psychosomatic illness is found in the early morning shifts. Human factors are connected with the severe operational errors in airline due to such conditions (Petrie and Dawson, 1997; Schroeder et al., 2006).

According to Blau and Lunz (1999), Burke (2003), Dunham (1977), and Shouksmith and Taylor (1997), shift work has been the most frequently used method of managing responsibilities and delegating authority/responsibility in communication, healthcare, transportation and manufacturing sectors and has had a tolling affect on the workers (Totterdell, 2005). Hence it is important to investigate the impact of shift work on employees' mental health. Jamal and Baba (1992) say that employees have not been able to cope with the pressure of work, hence suffer from extreme levels of stress. Barak (et al., 1995) explains that sleep disorders have been associated with shift work, which obviously creates a negative impression on how decisions are made.

The average shift of employees working in airline ranges in between 8 to 15 hours. Nevertheless, the normal time of shifts may be extended if any flight is delayed or workloads are altered on a continuous basis. It has also been found that fixed shifts do not create higher levels of job stress as the rotating shift does (Jamal and Baba, 1992). As a result of this, safety, which is a very crucial element in airline industry, is vulnerable to decision making processes affected by the shift work. Usually, employees experience negative effects in their well-being (Baba et al., 1998). Due to this, it is very important to reduce the negative impacts of shift work created on the employees working in airlines.

According to Baba et al. (1998), we see the current literature full of work relating to the role overload on stress, role variance, and role uncertainty, which are all classified as role stressors' or negative effects. Identifying what are the overall influences (long-term and short-term) of shift work on that relationship would be our main concern. Mental and physical health is severely affected by rotating shifts of employees in aviation (Baba and Jamal, 1991; Jamal and Baba, 1992; Totterdell, 2005). It is because there is inconsistent guidance and supervision to the employees in rotating shifts. Ultimately, role conflict and role ambiguity, along with heightened feelings are common in these shifts' employees in aviation. Furthermore, night shift staff often feels overloaded since the managers are only available during day shifts. No such managerial guidance exists in night shifts and that is why people in night shift have to look after matters on their own. Undoubtedly, night shift can be attributed to worsened job performance and decreased safety…