Inauguration of Celestia and Luna

"Well, it seems that former Princesses Celestia and Luna of Equestria left Silver Shoals since Twilight Sparkle decided to throw in the royal towel since that horrible war came to Harmonia. You see, these two sisters came to Nairobi for a meeting involving the crisis in many worlds, and soon, they decided to do a private inauguration in Sol Invictus One. That reminds me of the time when Lyndon B. Johnson got inaugurated as the US president after Kennedy was assassinated back then in Dallas, Texas."

--Su Ji-Hoon, In the Face of the Enemy

The inauguration of Celestia and Luna as the interim rulers of Equestria was held abroad Sol Invictus One at Moi Air Base in Nairobi, Kenya, following the shameful abdication of Twilight Sparkle earlier that day. This was the first non-scheduled, extraordinary coronation (in form of an inauguration) to take place in the history of Equestria.

It would be happened in during the USRAC War that abdication of Twilight Sparkle made Emperor Silbergeld knew weak spot of Canterlot's defensive.