Passenger jets have at least two engines. (The 747 has four.) Landing wheels come from four to six to a side, and even if they all should blow, a special foam can be sprayed on the runway to allow for "belly flops."
例如飛機的「心臟」﹘﹘發動機，至少都有兩個（波音七四七有四個，空中巴士 A 三○○有二個）；起落架上的輪胎，每邊各有四至六個；就算是全都爆了，也可以在跑道上加鋪一種高速膨脹泡沫，冒險以「狗爬式」迫降。