The email, both the title and body, explicitly states I've been selected for Flight 3 ("Halo Master Chief Collection Insider Program: Flight 3 - CONGRATULATIONS SPARTAN, You have been selected to participate in our third flight of the MCC Insider Program."), contains a complete rundown of this current flight, including the dates and times for all sessions this week, a message saying the download may not go up until the 3rd and will remain until the 9th, and a link to confirm my play sessions for this week.Did you get accepted into Flight #2? If not then you won't get access to Flight #3 untill next week sometime. If the email says your signed up to the MCC Insider Program then that does not mean you have access to the current flight as of yet.
As far as Flight 2 goes, that's a complicated question. I never got the initial email for that flight, nor was I ever able to download it, but I received all other correspondence for the flight, including an email asking me to confirm play sessions and another email with a survey asking about my experience with the flight. So something's fucked up with my status in the program.