Dozens of NASA's spaceflight missions that launched from Florida could be in jeopardy under a budget proposal from the Trump administration.

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.