First flight in the left-hand seat?

[Chris777]

How smooth is the promotion from first officer to captain?

Is it possible that, on the next commercial airline flight I take, the captain could be commanding the jet for the very first time?

Or is he/she supervised by a training captain on the first few flights as a captain? (and therefore there is no F/O on board, but two captains instead)

Thanks for your answers.
Chris