The Federal Aviation Administration can’t “keep pace with the commercial spaceflight industry” and “lacks the resources” to respond to mission changes, SpaceX said in a letter sent in response to $633,000 in federal fines for launching two missions with unapproved changes. SpaceX owner Elon Musk has promised to sue the agency, but it seems as if we’re still in the “strongly worded letter” phase of this particular feud.