# Tailoring In-Flight Food Consumption to Alleviate Fear of Flying Through Sensory Stimulation
## 2 Chemosensory Perception During Flights: Particularities of the Framework  
Traveling is one of the main activities in our daily lives. Human beings travel for work, healthcare reasons, shopping, amusement, and so forth, with different vectors depending on the purpose (and distance) they are traveling for. Specifically, when it comes to passenger transportation, a growing interest is paid from the customer to the experiential quality of the journey rather than only the final destination and costs [44], and this is expected to further increase in the near-future, with travel packages becoming increasingly tailored to the specific needs of the customer not only by offering competitive time/cost alternatives, but also adapting to the emotional expectations of the traveler. In such a framework, the amount of stress associated with air travel should be considered, caused by both environmental (dry cabin air, lowered cabin air pressure, vibration, background noise) and external (terrorism, viruses, accidents) insights, and possibly associated with customer satisfaction and travel choices. To this particular scenario, the role of the five human senses, and particularly of the two chemical senses, smell and taste, becomes highly relevant to ensure proper enjoyment of the flight experience; therefore, the tendency towards a real \"sensehacking\" becomes more and more popular, which is defined as the use of our senses, and sensory stimulation, in order to more intelligently help to improve our social, cognitive, and emotional well-being, in the relevant framework [45]. As said, emotions are conveyed to human beings through their senses, and chemical senses play an especially essential role in enabling significant sensory experiences. However, it is widely known that sensory perceptions are largely modified by the scenario in which human being is immersed. For example, it is well known that during space missions, due to microgravity, which induces physiological changes due to a shift of body fluids towards the head, the olfactory components activated during food consumption are diminished, leading to a modification in the flavor of food. Other phenomena affecting the chemical senses take place, such as space sickness, stress, radiation exposure, and psychological factors [46; 47]. For air passengers, it is well known that the limited space inside an aircraft and the ventilation systems commonly employed in modern planes make it difficult for a given airborne compound to dissipate, causing olfactory fatigue and habituation [48; 49]. Also, pressure variations in the cabin with respect to the pressure at the ground significantly modify the perception of a given compound, mainly modulating the absolute olfactory threshold, especially near the absolute perception threshold level [50; 51]. Similarly, concerning taste, air passengers experience a variation in their sensory perception, due to several factors, including the following: (i) air pressure that, when decreased, continues to decrease taste buds' sensitivity, requiring an increase in salt, sugar and herbs, and a reduction in sour taste, to produce a taste which is similar to the usual ones consumed on the ground [50; 52]; (ii) drop in humidity, which alters the sense of taste by drying out nasal passages and mouth [51]; (iii) psychological reasons, similar to those mentioned above for the sense of smell, that may further alter the production of saliva, in turn increasing the magnitude of the problem [53]. Furthermore, it has been observed that the role of engine noise is not negligible for sensory processing of food. In particular, loud noise appears to impair the perception of sweet and salty meals, at the same time enhancing the perception of umami flavor [54; 55], whose phenomenon can be used as a transformational device to facilitate palatable meals without boosting salt usage, which is deleterious for human health.