When any operator intends to overfly the United Kingdom carrying any package containing radioactive material with an activity greater than: (a) for special form 3000 A₁ or 100000 A₂, whichever is the lower; or (b) for all other radioactive material 3000 A₂, it must notify the Dangerous Goods Office (contact details as in GB 4) at least two working days before the expected date of the flight, providing the information required by 5;1.2.1.4 d), together with the names and addresses of the shipper and consignee, and the contact details for the operator. If the flight does not take place as planned, or if there are any changes in the information provided, the Dangerous Goods Office must be notified immediately. The operator is not required to wait for any acknowledgement or acceptance before carrying out the flight.