WASHINGTON, March 12 (Reuters) - Amazon.com ( AMZN ) drone unit Prime Air is withdrawing from the Commercial Drone Alliance, saying it had safety concerns that were incompatible with the group's positions.

Amazon Prime Air said in a letter seen Thursday by Reuters that the alliance's positions "on the most consequential safety questions facing the commercial drone industry are incompatible with Prime Air's core safety tenets."

The letter said that in over 70,000 drone flights, Amazon Prime Air's detect-and-avoid performed "successful collision avoidance maneuvers on two potential mid-air collisions with aircraft that could have led to catastrophic safety consequences, including the loss of life." Amazon ( AMZN ) said the alliance opposes requirements for the technology.