That's a very broad statement. Focusing on specifics would be more helpful. For example, 149 hours isn't that long, especially for aircraft which have high duty

That's a very broad statement. Focusing on specifics would be more helpful. For example, 149 hours isn't that long, especially for aircraft which have high duty cycle percentages. Why didn't the original test plan estimate how long it would take to find a certain percentage of [insert-bug-type-here], and find this issue? Would re-testing the code-base pro-actively find related latent issues? But none of these kinds of observations are fundamental. There's no general conclusion regarding software engineering to be drawn.