The objects falling out of the plane is chaff or window, which is long streds of aluminum. Welsh physicist, Joan Curran invented chaff during her time at the Telecommunications Research Establishment. The thin metal strips reflect the radio waves, and with the right conditions the reflected waves gives the impression that there is a large object on radar detectors. Thus, the Allies (mainly Great Britain, France, and the United States) had a way to distract the Axis (mainly Germany, Italy, and Japan) in battle. After multiple tests in 1943 the chaff was used on the battle field during Operation Gomorrah in Hamburg, Germany. Chaff's largest use was on June 5, 1944, the day before D-Day. The run included two chaff drops and dummy parachutists.
To learn more about chaff go to: https://www.smithsonianmag.com/innovation/woman-whose-invention-helped-w...
F/O L. Howard, No. 1 RAFFPU. [the Lancaster releases bundles of 'Window' over the target during a special daylight raid on Duisburg]. 1944. Photograph. Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Lancaster_I_NG128_Dropping_Load_... (Accessed January 3, 2019).