Key points. A public good has two key characteristics: it is nonexcludable and nonrivalrous. These characteristics make it difficult for market producers to sell the good to individual consumers. Nonexcludable means that it is costly or impossible for one user to exclude others from using a good.
Mechanical problems since they can be solved and have the second most deaths. I would have the plane go through at least 3 examinations before boarding then one passenger exam before takeoff.
