Elon Musk's threat Thursday to decommission SpaceX's Dragon spacecraft would have left NASA reliant on Russian capsules to get its astronauts into space.

Why it matters: Musk's rift with President Trump exposes how reliant NASA has become on a single private sector partner to reach the International Space Station after ending the space shuttle program in 2011. • Musk eventually walked back the threat Thursday, but it demonstrates how critical SpaceX is to the American space program.

Catch up quick: The feud between the president and world's richest man exploded into public view Thursday after Musk criticized Trump's flagship spending bill. • Trump subsequently threatened to cut all of Musk's government contracts, and Musk retaliated by threatening to mothball SpaceX's Dragon. • It'

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