The company said in a statement that Stephenson stepped down in order to devote more time to AT&T. Stephenson told Boeing that 2018 "will be an extremely busy one for him at AT&T."
Last month, the Justice Department filed a lawsuit in an attempt to block AT&T's proposed merger with Time Warner. The department argued that the $85 billion deal would raise prices for consumers and stifle competition.
AT&T has said it would fight the lawsuit and resisted suggestions that it should sell off some of its businesses to more easily obtain regulatory approval.
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