Which operation involves helicopter supply to seaborne vessels?

The operation that involves helicopter supply to seaborne vessels is known as VERTREP, which stands for Vertical Replenishment. This method utilizes helicopters to deliver supplies, equipment, and personnel directly to ships at sea, making it an efficient means of resupplying naval or research vessels that may be in remote locations or on the move. VERTREP can be particularly advantageous when weather conditions or the ship's operational tempo make traditional supply methods, such as alongside replenishment, impractical or impossible.

In contrast, other options include UNREP (Underway Replenishment), which typically involves refueling and resupplying vessels while they are both underway, but does not specifically utilize helicopters. NCAGS (NATO's naval Cooperating Guidance Service) relates to cooperative planning and efficiency in naval logistics rather than direct supply operations. NDRF (National Defense Reserve Fleet) pertains to a fleet of vessels reserved for national defense purposes and does not specifically involve helicopter resupply operations. This clarity distinguishes VERTREP as the operation specifically associated with helicopter supply.