No (sooner) had the plane’s wheels (touched) the ground (when) i heard the chimes of cell phones (throughout) the cabin. (no error)
the answer is (when) but why is that so? what kind of error is this???

This is an idiom. It goes like this: “No sooner ___ than ___.” Example:

No sooner had I arrived at the ballpark than it started to rain.

It means that the second thing mentioned happened right after the first. In my example, I arrived at the ballpark, and then it started to rain basically right away.