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.