Whitley test "produced a failure at 98% of the design load" is that good?

[Observer1940]

I have acquired an old Armstrong Whitworth Aircraft Ltd book and in the part about fuselages it states regarding the Whitley:-

"A full scale test at R.A.E. produced a failure at 98% of the design load."

Are there any aircraft engineers out there, as I would have thought that an aircraft must meet, or exceed 100% of its design load to be airworthy especially when it would be required for AWO (all weather operations)?

Although I understand the design loading is higher than the design load for level flight, due to the necessity to be able to dive the aircraft, pull the aircraft out of a dive, make manoeuvres and turn, it is clear that the Whitley failed on test at "98% of the design load."

Also you have weather forces, icing and turbulence to contend with too.

Any comments?

Mark