Anyone can feel weightless by falling. During the zero-gravity portion of the flight, the plane flies toward the ground at the same free-falling speed and acceleration as the passengers. ---taken from the NYT
= ...plane flies toward the ground at the same free-falling speed and acceleration as the passengers did.
As you know, I can fully understand its meaning and know the quote is perfectly correct, but I have no idea about why the verb(=did) of the subordinate clause can be dropped. Did you know any relevant grammar rule about this kind of omission? Thanks in advance.
Merry Christmas and Happy New Year
According to Michael Swan's Practical English Usage: We can leave out words after as and then, if the meaning is clear. (177.7)
It goes on to give some examples of leaving out verbs and subjects. For example,
The food this year is as good as last year's (food).
I scored more points in PacMan than you (did).
Hope this helps, have a happy holiday!
Thank you, macanudo and ymnisky, I've got it.