Flyvefisken-class (Standardflex 300 or SF300)

The Flyvefisken class, also designated Standard Flex 300 or SF300, was developed for the Royal Danish Navy to replace the Søløven-class torpedo boats, Sund-class coastal minesweepers, and Daphne-class seaward defense craft. Fourteen vessels were completed between 1985 and 1995, with the first ship entering commission in 1989.

The design utilizes a modular system known as StanFlex, which incorporates a standard hull design with interchangeable containerized weapon and sensor systems. These containers allow the ships to be reconfigured for different roles, typically within 48 hours. One container position is located on the foredeck, with three additional positions on the quarterdeck. The hull and superstructure are constructed using a sandwich principle of fiberglass layers over a PVC cell foam core. This construction method was adopted to reduce maintenance requirements. The ships are configured to perform four primary roles: surveillance and pollution control, combat, mine countermeasures, and minelaying.

In the combat role, the class utilizes guided missiles rather than the hit-and-run torpedo tactics of its predecessors. For mine countermeasures, the ships use side-scan sonar and remotely operated vehicles to locate and neutralize mines individually. In Danish service, the ships were produced in three series, with variations in their propulsion and auxiliary engine configurations. Series 1 includes hydraulic propulsion, while Series 2 and 3 feature additional auxiliary engines.

The class has been operated by the Royal Danish Navy, the Lithuanian Naval Force, and the Portuguese Navy. Lithuania acquired four vessels between 2007 and 2016. Portugal purchased five vessels in 2014, designating them the Tejo class. Of these, four were reconfigured for active service and one was used for spare parts. Portuguese vessels are tasked with policing the exclusive economic zone near Madeira. In 2023, 13 sailors assigned to the NRP Mondego were relieved of duty after refusing to board the vessel, citing claims regarding its seaworthiness during a mission to monitor a Russian ship. One Danish vessel, the Søløven, was converted to a diving support role in 2012.