Happens all the time.

Both asleep, though, is a big problem. About ten years ago there was a (Delta?) flight to Vegas (?) with both pilots asleep. They flew past their destination and went on their merry way until a flight attendant check up on them.

> flew past their destination and went on their merry way until a flight attendant check up on them.

That... doesn't seem like a great illustration of why both pilots asleep is a big problem :)

They overshot the airport by about 40 minutes, which means they had to fly an extra 30 minutes back. Every minute the flight attendant delays in waking up the pilot is doubled.

That's not a huge deal in Vegas, but if you miss Honolulu that's a big problem.

Sounds like it: "The PIC then asked permission to rest from the SIC and was granted. A few seconds later, the PIC slept and the SIC then took over the PIC duty as PM."