## 2 Materials and Methods
### Experimental Procedure and Design  
We selected the traditional control tower at JianDe General Aviation Airport and the remote tower at the Zhejiang Provincial Flight Service Center as the testing environments to ensure the reliability of the experimental results. We obtained the sample data from 10 controllers (8 men and 2 females) associated with the unit, whose ages ranged from 25 to 50 years.  
We briefed each participant on the experimental protocols and equipment operating techniques prior to the evaluation to mitigate any extraneous variables that may influence the findings. Furthermore, we instructed participants to avoid strenuous activity prior to data collection and to ensure adequate rest and sleep. Figure 1 depicts the experimental setup.  
The experiment required all subjects to use the Tobii pro eye-tracker and the heart rate monitoring device under normal conditions for 30 min each. We conducted the trials in  
Figure 1: Remote Tower Test Environment.  
real time, using a limited number of randomly placed aircraft to avoid disrupting the air traffic controllers at the general aviation airport during the tests. The measures sought to maintain a comparable workload for each controller, entailing the oversight of 2-3 aircraft in clear to partly cloudy weather circumstances.  
In order to ensure the accuracy of the experimental results, factors that might affect the fatigue state of the controllers were strictly controlled. In terms of scheduling, the normal state experiment was scheduled between 8:00 a.m. and 11:00 a.m. This is because at the beginning of a workday, controllers are usually energetic and can be in a relatively stable non-fatigue state. The fatigue experiment was scheduled between 1:30 and 5:00 p.m. on the other day because, according to the pre-test survey, all participants had a habit of taking a nap, and conducting the experiment in the afternoon would make the participants more likely to be in a fatigued state.  
Prior to the experiment, we standardized participants' daily activities. Participants were asked to maintain a normal work and life rhythm the day before the experiment, and to avoid overexertion or strenuous exercise. At the same time, we recorded the participants' sleep to ensure that they had enough sleep before the experiment. During the experiment, we provided participants with the same experimental environment, including consistent conditions of temperature, humidity, and light to minimize the influence of environmental factors on the fatigue state. In addition, we controlled the difficulty and duration of the experimental tasks to ensure that each participant performed the experiment under the same task load, so as to more accurately assess the effect of fatigue on situational awareness.  
Furthermore, we categorized participants as experienced or trainee controllers based on their tenure. Matter controllers are those who hold a full controller's license issued by CAAC and have \(\geq\)5 years of frontline tower control experience. Trainee controllers are those who have completed the basic control training and passed the examination, but have less than 1 year of accumulated practical experience. The population distribution of controllers is shown in Table 1.  
We terminated the recording of ocular movements and cardiac metrics after a total measurement duration of 30 min. Every 10 min, we documented the participants' performance and continued to observe pertinent facts related to their tasks. The supervisor evaluated the participants using the working memory assessment scale and the communication and coordination assessment scale. After the participants switched roles, the supervisor distributed subjective questionnaires and repeated the aforementioned data collection procedure with each participant.  
The eye movement data were processed using Ergolab software v3.14 at the end of the trial, and outliers in the HRV data were corrected by Kubios HRV Premium software--Kubios HRV 2.2.