So thaaaat's where they were going!

X17 photographers snapped the Kardashian Klan boarding a private jet bound for San Francisco Monday afternoon (see the gallery below) and while a G4 would be enough of a surprise for most, that wasn't all Kanye had in store for Kim and her family ...

Kanye West rented out AT&T Park, home of the Giants, and got down on bended knee in the middle of the field, family and friends and a full orchestra watching, and PROPOSED to Kim Kardashian!!!

And guess what? She said yes! Yeah, big surprise. And guess what? It's a 15-carat diamond! Yeah, big surprise. Still, it's cute, right?

It'll be the third time (a charm?) for Kim and the first marriage for Kanye. And coincidentally it was Kim's 33rd birthday yesterday. Not a bad birthday surprise!