The term 'grounded' is often used but frequently misunderstood. Hope this helps:
Grounded Aircraft | Aircraft | Operations and Safety
GROUNDED AIRCRAFT
An aircraft requiring modification or repair may become "grounded" until the necessary work has been completed and the aircraft is once again fit for flight.
In many cases, the work is concluded within a few days and the Certificate of Airworthiness (CofA) or Permit to Fly will be re-validated by the maintenance organisation responsible.