During World War II, Operation Overlord, the campaign to invade Normandy, France, began on June 6th, 1944, popularly known as D-Day. Although famously conjuring up images of massed troop landings on the beaches and ferocious hand-to-hand fighting in the German coastal fortifications, D-Day actually began in the dark around 1 AM in the skies above Normandy.

The plan consisted of over 13,000 members of the 82nd and 101st airborne divisions to make night parachute drops behind the German lines. Their missions:
While the objectives were not completed as originally planned, the parachute drops were vital to the success of the D-day landings.
There were many reasons that the parachute drops that began D-day were not as effective as predicted or planned for.
The above factors made many airplanes make second and third passes over the drop zones, exposing them to increased German anti-aircraft fire and resulting in drops which were not at correct altitudes and speeds.
An attempt was made to pre-drop “pathfinder teams” using a primitive radar beacon that would help the planes home in on their drop zones. Several issues rendered this preparation measure ineffective:
These issues contributed to the confusion in making the parachute drops.
Mission Albany, assigned to the 101st Airborne Division, began at approximately 1:00 AM on June 6, 1944. Several regiments arrived at the wrong jump zone too near the beaches and others were scattered and forced to fight small unit actions while trying to reach their objectives.
The main objective of capturing the la Barquette lock and two foot bridges was accomplished by 4:30 that morning. Another major objective, the capture of the town of Saint-Come-du-Mont and destroying bridges over the River Douve was not accomplished in spite of a day long battle.
Mission Boston, assigned to the 82nd Airborne Division, began drops lightly before 2:00 AM. The failure of the pathfinder teams to be able to adequately mark drop zones led to many groups dropping into swampland and losing much of their support equipment.
A primary objective of capturing the town of Saint-Mere-Eglise was accomplished on time, and they successfully defended against German counterattack.
The assigned objective of destroying the bridges over the River Douve was not accomplished. However, a makeshift battalion seized a hilltop and disrupted German attacks near the landing areas for three days until relieved from the beaches, accomplishing their mission although not in the manner anticipated.
As a result of the above mentioned issues with weather, lack of coordination and drop zone errors, the parachute assault that was the real beginning of D-Day did not live up to the strategic success that the Allied command structure had planned for.
Despite all of the difficulties, however, German forces were not able to take advantage of the piecemeal parachute forces. Some of this was because there was a lack of cooperation within the German command structure and some due to great levels of initiative and bravery on the part of the paratroopers.
Allied forces rallied quickly following the drop problems and many small unit actions were fought over both the objectives and also wherever they happened to encounter German forces. In the end, the airborne forces linked up with the troops moving inland from the beach landing areas. All German forces in the initial landing areas were defeated within the first week of combat.
The airborne assault that began D-Day most certainly could have gone better; but, in the end, achieved its overall goals.