求助英语语法

Question

First two hours, now three hours—this is how far in advance authorities are recommending people show up to catch a domestic flight, at least at some major U.S. airports with increasingly massive security lines.这句话中的show up怎么解释？求大神分析一下语法。

Answer 1

前两个小时，现在是三个小时——这是当局建议人们出现在国内航班上的时间，至少在美国一些安检队伍越来越密集的主要机场是这样。
First two hours, now three hours状—this主 is系 （how far in advance authorities are recommending people show up to catch a domestic flight, at least at some major U.S. airports with increasingly massive security lines表语从句).
（how far in advance状语） （authorities主）（ are recommending谓语） （people show up to catch a domestic flight, at least at some major U.S. airports with increasingly massive security lines宾语从句）
people主 （show up谓语：省略should的）（ to catch a domestic flight目的状语）, （at least at some major U.S. airports with increasingly massive security lines状语）宾语从句