Your goal is get out of way. On the runway you can't go lower, you can't maintain level (you never can be sure how far and how fast the incoming plane), you can't go to the side (rudders are an option but you need to be airborne and be sure you still have the time, see level) so your only option is to go up and then go to the side.
> out of surprise
Less of surprise, more of need to take an immediate action, again you can't judge the speed and distance of the airplane of unknown (and often even known) type. To see how hard it is search Youtube for aircraft carrier landings videos.
Your goal is get out of way. On the runway you can't go lower, you can't maintain level (you never can be sure how far and how fast the incoming plane), you can't go to the side (rudders are an option but you need to be airborne and be sure you still have the time, see level) so your only option is to go up and then go to the side.
> out of surprise
Less of surprise, more of need to take an immediate action, again you can't judge the speed and distance of the airplane of unknown (and often even known) type. To see how hard it is search Youtube for aircraft carrier landings videos.