V - 1 flying bomb facilities In order to carry out the planned V - 1 " flying bomb " attacks on the United Kingdom , Germany built a number of military installations including launching sites and depots . Some of the installations were huge concrete fortifications . The Allies became aware of the sites at an early stage and carried out numerous bombing raids to destroy them before they came into use . Production . The unpiloted aircraft was assembled at the KdF - Stadt " Volkswagenwerke " ( described as " the largest pressed - steel works in Germany " ) near Fallersleben , at Cham / Bruns Werke , and at the Mittelwerk . underground factory in central Germany . Production plants to modify several hundred standard V - 1s to Reichenberg R - III manned aircraft were in the woods of Dannenburg and at Pulverhof , with air - launch trials at Lärz and Rechlin . Flight testing was performed by the Luftwaffe at Peenemünde West and , after the August 1943 Operation Hydra bombing , at Brüsterort . Launch crew training was at Zempin , and the headquarters for the operational unit , FR 155 ( W ) , was originally based at Saleux , near Amiens , but was subsequently moved to a chateau near Creil ( " " FlakGruppeCreil " " ) , with the unit ' s telephone relay station at Doullens . Other V - 1 production - related sites included a Barth plant which used forced labor , Buchenwald ( V - 1 parts ) , and Allrich in the Harz . In addition to the storage and launching sites listed below , operational facilities included the airfields for Heinkel He 111 H - 22 bombers which air - launched the V - 1 from low altitude over the North Sea . The ten - day - long aircrew training was at Peenemünde , and the bases were in Gilze Rijen , Holland for launches through 15 September 1944 , and in Venlo for launches after the 1st week in December . Aircrews were billeted five miles away at Grossenkneten for secrecy . Storage depots . To supply the V - 1 flying bombs launch sites in the Calais region , construction was begun on several storage depots in August 1943 . Sites at Biennais , Oisemont Neuville - au - Bois , and Saint - Martin - l ' Hortier were never completed . The completed sites were : For serving the ten launch sites planned for Normandy , a depot was constructed at Beauvais . It was bombed June 14 , 15 & 16 1944 A depot to serve Cherbourg launches was near Valognes . By February / March 1944 , a plan for three new underground V - 1 storage sites was put into effect . The Nucourt limestone cave complex between Pontoise and Gisors was bombed on June 22 , 1944 with 298 V - 1s buried or severely damaged . One in the Rilly - la - Montagne railway tunnel was attacked by the British with the Tallboy earthquake bomb s on July 31 collapsing both ends of the tunnel . The Saint - Leu - d ' Esserent mushroom caves was the largest of the underground V - 1 sites . It was attacked by No . 617 Squadron RAF with Tallboys on 4 July . A larger " Heavy Crossbow " bunker was built at Siracourt , between Calais and the river Somme , as a V - 1 storage depot . RAF records refer to flying - bomb stores at " Bois de Cassan " ( bombed August 2 – 4 , 1944 ) , " Forêt de Nieppe " ( bombed July 24 , 25 , 31 , August 3 , 4 , 5 , 6 , 1944 ] and " Trossy St . Maximin " ( bombed August 3 – 4 , 1944 ) V - 1 launching sites . V - 1 launching sites in France were located in nine general areas - four of which had the ramps aligned toward London , and the remainder toward Brighton , Dover , Newhaven , Hastings , Southampton , Manchester , Portsmouth , Bristol , and Plymouth . The sites on the Cherbourg peninsula targeting Bristol and Plymouth were captured before being used , and eventually launching ramps were moved to Holland to target Antwerp ( first launched on 3 March 1945 from Delft ) . Initially the V - 1 launching sites had storage buildings that were curved at the end like snow skis ( " ski sites " ) . An October 28 , 1943 intelligence report regarding construction at Bois Carré near Yvrench prompted No . 170 Squadron RAF reconnaissance sortie E / 463 on November 3 which detected " ski - shaped buildings 240 - 270 feet long . " By November 1943 , 72 of the ski sites had been located by allied reconnaissance , and Operation Crossbow began bombing the original ski sites on December 5 , 1943 . Nazi Germany subsequently began constructing modified sites with limited structures that could be completed quickly , as necessary . This also allowed the modified sites to be quickly repaired after bombing . However , the work to complete a modified site before launching allowed the allied photographic interpreters to predict on June 11 , 1944 that the V - 1 attacks would begin within 48 hours , and the first attacks began on June 13 .