The term 'OPENING NOTES' can be solved by the four-letter word 'DORE'. This is an acronym for 'Drop On Requested Entry', which is a type of air traffic control procedure. In this procedure, an aircraft is instructed to descend to a lower altitude when it reaches a certain point in its flight path. This is done to ensure that the aircraft is at the correct altitude when it enters the airspace of the destination airport.