I didn't know that the default was open seating.

我不知道默认是开放式座位。

Trains have a mix of open seating and more private compartments.

火车混合了开放式座位和更多私人车厢。

In this case, the normal way that things happen on the airplane is " open seating."

在这种情况下， 飞机上发生事情的正常方式是“开放式座位” 。

Open seating is a system where there are no seats that are reserved, or we might also say " assigned (assigned) to someone."

Open seating 是一种没有预留座位的系统， 或者我们也可以说“分配（assigned）给某人” 。