What does the word it refer to in the following sentence? Does it refer to the missing plane or the act of the search?
The focus of the search has moved several hundred miles west of the course it should have been following.
The sentence above is from the following paragraph:
Vietnam is scaling back its air and sea search for missing flight MH370 as China said it will step up its search and rescue efforts to include land areas.While Vietnam's deputy transport minister said it was suspending search and rescue operations, China said it will add two planes to its search for the missing passenger jet and its 239 passengers and crew. The focus of the search has moved several hundred miles west of the course it should have been following.