Germanwings co-pilot Andreas Lubitz tested what would be deadly descent settings on the flight that directly preceded the one investigators say he deliberately crashed into the French Alps. That detail comes from a 29-page interim report released today by France's BEA crash investigation agency; it describes how Lubitz, flying from Dusseldorf to Barcelona, put the plane in a "controlled descent that lasted for minutes and for which there was no aeronautical justification" on the same day that he brought the plane down on its return journey. The AP reports the pilot had left Lubitz alone in the cockpit, during which time he moved the plane into descent mode five times in less than five minutes. After each descent, he brought the plane back up to regular altitude.
"I can't speculate on what was happening inside his head; all I can say is that he changed this button to the minimum setting of 100 feet and he did it several times," says BEA's director. The Wall Street Journal specifies that during a 4.5-minute period, Lubitz keyed in altitudes ranging from 1,000 feet to 49,000 feet. Investigators say the adjustments were made while the plane was descending from 37,000 feet to 35,000, so they apparently went undetected by the captain and others on the flight; air traffic controllers didn't notice them, per the New York Times. The new information comes via that flight's black box. Reuters notes the BEA's final report won't be finished for a year. (Read more Germanwings crash stories.)