The "bubbling and blistering" that was earlier observed on certain models of F-35 jets after prolonged flights is not noticeable to the human eye and the entire issue should be viewed in a broader context, Lockheed Martin test pilot Billie Flynn told the website Defence News. At the same time, he cited engineers as saying that if an F-35 jet is to serve for decades, the exposure to extreme conditions causing such problems should be dealt with.
"I don’t know if I really ever saw much after a flight. I just knew that our engineers had told us about [the problem]. An engineer […] would see that it would be hotter than they predicted, which would lead them to tell us: 'If this airplane is going to last 40 years long, then we have to manage this exposure'", Flynn said.
The pilot went on to notice that the bubbling and blistering only appeared on F-35B and F-35C jets after prolonged missions, which rarely occur in real combat scenarios. Flynn said that he knows of no "combat scenario" where a jet would be subjected to this kind of environmental stress.
"Make a run at 700 knots, make another run at 700 knots, go to an aerial refueling tanker, get fuel for myself […] and then race out again and again and again. Repeat this cycle for four- and five-hour missions. [...] That’s extreme speed, and that’s repeated flights in those environments", the test pilot added.
The issue was first reported by Defence News back in 2019 and was classified as a Category 1 deficiency by the Pentagon soon afterwards, meaning that the US military considered it a serious threat to operating the fifth-generation aircraft. However, as of December 2019, the issue is considered to be "closed", although no solution was rolled out. The F-35 Joint Program Office stated that the advantages of fixing the issue were not worth the costs.
Instead, the Pentagon suggested limiting the time pilots can spend at hypersonic speeds with full afterburner on to less than a minute, as this would prevent permanent damage to the F-35's stealth coating, which reduces the jet's visibility to radars.