At this time efforts were made to strengthen the MLD in the Dutch East Indies, but when the Japanese invaded they had to withdraw to other Allied countries. On March 3, 1942, nine MLD Dornier and Catalina flying boats were destroyed in the Japanese air attack on Broome, in Australia. An unknown number of MLD personnel were killed. Later, in Ceylon, 321 Squadron was re-formed under the command of Willem van Prooijen, with MLD Catalinas.
The Royal Netherlands Military Flying School was established in the United States, at Jackson Field (also known as Hawkins Field), Jackson, Mississippi, operating lend-lease aircraft, training all military aircrew for the Netherlands. The intention was to return to the Netherlands and to participate in the war against Japan. After liberation, the main MLD base was established at Valkenburg, with De Kooy as the overhaul and repair base.
The main roles of the MLD were maritime patrol, anti-submarine warfare and search and rescue. From 1953, with the creation of NATO, the MLD received substantial aid from the USA, including PV-2 Harpoon, P2V Neptune and TBF Avenger aircraft.
In the late 1960s, the aircraft carrier was replaced in the anti-submarine role by a squadron of Westland Wasp helicopters operated from anti-submarine frigates. These helicopters were replaced by Westland Lynxs and these will be replaced themselves by NH-90 helicopters.
In 2003 it was announced that Naval Airstation Valkenburg would close in 2006. All P3C orions were sold to the German and Portugese Navy's, Naval squadrons 320 and 321 were disbandend.
In 2008 the navy helicopters (westland lynx) and crew of naval squadrons 7 and 860 based at NAS de Kooy were officially transferred to the defence helicopter command (DHC) as were the Dutch airforce helicopters. All Dutch military helicopters are now under one single command which is officially neither navy nor airforce. squadron 7 is to become a small training squadron, squadron 860 will become much larger and is desginated to be DHC's maritime squadron with a large navy component. NAS de Kooy was renamed Maritime Airstation de Kooy.