I have a cousin (now in his 50s) who freezes when startled.
He gave up motorcycles at 19 after a near miss (his bike went under a bus, and was crushed as the bus rolled over it, but he bounced-off the bus wheel and didn't go under) and sticks to driving a car. He is a careful and reserved driver but has been involved in numerous accidents that the insurance companies see as "not his fault" - such as a car pulling out of a junction ahead of him and he ploughs into it; accidents that would have been avoided if his reaction was other than "rabbit in the headlights".
If someone reacts to surprise by freezing, I would not be asking them if they wanted to think about training for a flight license.