That's a good question. First of all, none of that happened in flight. We have six test articles that we'll never fly. They go through very extensive ground testing. We put them in fixtures, and we cycle them through two lifetimes of use. That's 16,000 hours.
As we go through that cycle, we look for cracks. By the way, we like to find cracks. If we don't find any cracks and the airplane looks perfectly normal, you are probably going to find cracks later on when it's actually in flight. So we do that test very specifically to find these areas in the airframe that may be slightly undersized for the loads they're going to experience.
We found one. It was in the frame of the STOVL airplane, as you mentioned. That frame in the STOVL jet is made of aluminum. That frame in the air force jet is made of titanium, so it's a whole different metal, with different crack propagation and a different stress pattern and everything else. However, we did stop the air force testing until we could go back and do a full analysis of the air force frame and compare it with the Marine Corps frame. This is not a big deal. It's often trumpeted as being a big deal, but these are the kinds of things that you find in tests and that you fix to make sure you don't have any of these shortfalls when the airplane finally gets into the hands of the operator downstream.
We are working very closely right now with Héroux-Devtek, which is the manufacturer of those frames, to get a solution in place. The frames that are on the airplane will be repaired and returned to service. Then we'll be back in testing just after the first of the year. For those that are not built yet, it is a very simple software change to a tape that cuts a new frame. All the airplanes in the future will have the changes in them.
So we want to find these things and we want to find them now. We don't want to find them later. We don't want to have airplanes that are going to experience the cracks later.