## 2 Literature Review
In addition to training pilots and flight crews, VR is used to educate passengers about aviation safety. In the development of virtual environment, [PERSON] and [PERSON] [9] presented an immersive HMD-based game that allowed passengers to experience multiple aircraft emergencies to show how to survive. At the same time, they compared this educational approach with the traditional method (safety cards) typically used by airlines. The HMD-based game turned out to have more detailed information. [PERSON] et. al. [10] used VR techniques to design a mobile VR tool and evaluate the effectiveness of this tool between the safety education tools used by airlines. Sixty-eight participants, aged 20-24, were divided into two groups (app group and card group). The results shown that the app was more engaging than the card. Besides, instructions given by the app were perceived as more effective than those of the card. Moreover, after using two instructional media, participants in the app group were able to don the life preserver in less time than those in the card group. [PERSON] and [PERSON] [11] examined the efficacy of a virtual reality (VR) cognitive health screening tool (integrated into simulated flight scenarios) in identifying general aviation pilots who experienced a critical incident during flight in a full-scale Cessna 172 simulator. The fifty-one participants were between 17 and 71 years old, and they were divided into two groups: under 50+ years old group and 50+ years old group. During the VR cognitive screening, user-experience queries were incorporated into the screening process to investigate whether older, as compared to younger pilots would experience cybersickness. There was no significant difference in flight simulator preference, with both older and younger participants mostly preferring the VR system over the standard simulator. On the other side, the results also showed better piloting performance in the VR test predicted critical incidents from the quasi-real world flight simulation. Maintenance is also important in the aviation industry. Using VR as a maintenance training tool provides a safe learning environment that minimizes the risks that may occur during training with significantly reduced costs. [PERSON] et al. [12] proposed a virtual teaching and training system to meet the needs of modern aeronautical engineering education. The method was compared with traditional methods for several factors such as learning efficiency, cost, achievability, and convenience and showed positive results. [PERSON] et al. [13] used HTC VIVE and Leap motion to develop an aircraft virtual equipment maintenance system based on gesture recognition to improve employees' understanding and maintenance skills. [PERSON] et al. [14] used VR for training smart aviation maintenance training service for aircraft's preflight check. In fact, although engineers are trained in a highly secure environment, there is still some training that can be potentially dangerous in hazardous environments, such as practicing in certain fire and explosion situations, inspecting and repairing fuel system components in the dark, and small spaces in the wings. Meanwhile, using VR, engineers only need to be in a secure small area to sit still or move around, but still be able to train in the same situations in the virtual environment. Aircraft models and aircraft parts required for aviation training are often very expensive. In addition, mistakes inevitably occur during training, which can lead to equipment damage. Instead, through VR, engineers will be trained on 3D models, minimizing errors that lead to failure and lowering training costs. Another problem that can be solved is that engineers will have more time and chance to practice, thus increasing the effectiveness of the training program.