A quick analysis of past announcements shows SpaceX misses major milestones by about 2 years.

SpaceX is well-known for its ambitious timelines. To be fair, they're in good company on this front: many spaceflight firms, and also NASA, are similarly guilty of underestimating how long major projects will take. That's why NASA's science programs—and more recently, its human spaceflight programs—use a metric called the Joint Confidence Level, or JCL, to calculate the odds something will be delivered on time based on available funding levels. In short, NASA doesn't commit to a launch date until a JCL analysis says there's a 70 percent chance it will hold.

I went through SpaceX's past press releases and official statements to see if I could quantify the average delay time for major milestones. I found that on average, SpaceX misses publicly stated deadlines by an average of 2.1 years.

Here's the dataset. Some well-known examples of these delays include the first crewed Dragon flight (originally promised in 2014, but yet to occur) and the Falcon Heavy (originally promised for 2013 or 2014, but yet to launch). Again, to be fair, an analysis of other NewSpace companies or NASA would likely turn up similar results. But that doesn't make it any less true.

The GAO thinks SpaceX may not be certified for ISS crew rotation flights until 2019.

On February 16, the Government Accountability Office released a report saying SpaceX and Boeing might not be certified to fly ISS crews until 2019.

Before NASA signs off on SpaceX for astronaut transportation, the company must conduct two demo flights of its new Crew Dragon spacecraft. The first will be an uncrewed test flight, which SpaceX expects to occur in November. The second will take place with two astronauts, and SpaceX says the mission will be ready to fly in May 2018.

The GAO is skeptical of those dates. Among the reasons: SpaceX plans to make two more upgrades to the Falcon 9 this year, before showing NASA the rocket's design is finalized and stable—prior to the November uncrewed test flight. There's also an ongoing debate about the company's plan to fuel the rocket with astronauts aboard, and questions about the significance and mitigation of cracks found in Falcon 9 engine turbines.

SpaceX Preisdent Gwynne Shotwell recently told reporters at Kennedy Space Center she was confident the first crew flight would occur in 2018. If that happens in May as scheduled, NASA certification could come between July and September, followed by the first official ISS crew rotation flight.

Where, exactly, the Moon tourist mission would fit in to that schedule is unclear, considering the company has a backlog of other missions to fly after last year's launch pad explosion. In theory, SpaceX could proceed with the flight anytime—it's just a question of whether they are potentially willing to risk looking bad in the context of their NASA partnership.

Flying tourists after the first paid ISS crew rotation flight would seem to be the most prudent; NASA has been without the capability to launch its own astronauts since the space shuttle retired in 2011. The agency made a big bet on commercial crew providers after canceling the Constellation program in 2010. As of last year, NASA still provides the bulk of SpaceX's revenue, and in Monday's announcement, SpaceX went out of its way to thank the agency for shouldering most of the development cost of Crew Dragon.

NASA, meanwhile, has been forced to lay the groundwork for using Russian rockets to reach the ISS in 2019 (ironically, the seats are being purchased through Boeing) in the event SpaceX and Boeing crew flights are delayed further.