The speaker says aircraft could be made with less suitable metals, but would then consume more fuel and fly less efficiently.

“Like you can't use aluminum. I mean, aluminum is a great metal for making aircraft because it's sort of light and durable and so on. But you can't imagine that you make aircraft with like worse metals and then it just takes more fuel and it's like less efficient to fly.”

“So there's a sense in which you can compensate and”