## 2 Materials and Methods
### Experimental Design  
The experiment implemented a two-factor (2 \(\times\) 3) within-subjects design, with air route alternation and display design serving as independent variables. The two levels of the air route alternation included the air-route-as-planned condition and air-route-altered condition. Under the air-route-as-planned condition, participants were asked to keep the flight attitude parameters (including speed, altitude and course) according to the initial task plan, in which participants were required to make the speed and altitude reach the preset target values at all six observation time nodes (\(T_{1}\)-\(T_{6}\)) and to keep the initial course unchanged (Figure 2). In the air-route-altered condition, participants were asked to execute a task plan that was the same as the one in the air-route-as-planned condition at the beginning. Afterwards, the plan changes would occur during the flight simulation, and the participants were required to make air route alternation according to the new situation, in which the target values of speed, altitude or course changed at all six observation time nodes (Figure 2). Specifically, when the target course was changed, the participants were asked to turn the steering wheel in the correct direction (left or right) and to rotate horizontally until the new target course was reached. When the target speed was altered to a larger (or smaller) value, the participants were required to push forward (or pull back) the thrust levers and retract (or release) the flaps to accelerate (or decelerate). The participants were supposed to pull back or push forward the steering stick in a proper range to climb or descend to a new altered target altitude. Under the air-route-as-planned condition, the target course remained fixed; the target speed and altitude were set consistent with the task plan given before experimental task. The participants were supposed to mainly concentrate their visual attention on the PFD, excluding the ND, and to manipulate the handheld devices, excluding the steering wheel; thus, the eye-hand coordination was challenged at a lower level and the precision of task performance was of higher accessibility. Under the air-route-altered condition, all three flight attitude parameters were changed and different from the previously informed task plan. The participants were required to allocate their visual attention to both the PFD and ND, and to simultaneously manipulate all the handheld devices, leading to more challenges in eye-hand coordination and the precision of task performance. The interface used in laboratory experiment research is usually extracted or simulated from actual scenarios [28; 32; 41], and different display designs of the flight parameters presented on the simulated flight platform also influence the participant's interactive behavior. In our experiment, three typical types of interface designs derived from civil aviation were examined, which varied mainly based on the design of the PFD, including Interface 1 (center-layout with a low-salience design, simulating an A320), Interface 2 (center-layout with a medium-salience design, simulating a B737) and Interface 3 (off-center-layout with a high-salience design, simulating an ARJ-21). Obvious differences existed in the information layout and information visual coding among the three simulated interfaces. In Interface 1, the indicator of attitude (pitch and roll) was set in the center and the compass was of small size; also, the altitude was displayed in the open window digital indicator while the speed in the low-salience indicator was displayed without an open window design. In Interface 2, the information layout was similar to Interface 1, while digital displays of both the altitude and speed indicator were window designed.