Most people (profile and ed the exception) don't start a loop at probably less than 150 ft high. At 60 mph (very slow speed for most anything) from the second you start to pull a loop, in less than 3 seconds (264 ft) you're over 400 ft (150+264 @ 60mph). Most people training fly around 300+ and that's before they freak and go up then straight down They blow through the 400 ft mark all of the time. Imagine the instructors frustration.

At 80 mph you're going 117 ft per second.. Very easy to blow through the 400 ft.

Think about 120 @ 176 ft second and for jets, 180 mph @ 264 feet per second.... If my math is correct that is..