What has Old/Young got to do with it? There are plenty of 50-year-old/200 hour FOs flying with 25-year-old/4000 hour Captains. The only rule is that two age 60+ can't fly together.
Do you mean Experieced/Inexperienced?
Operations manual Part A is the document you're looking for. It will describe flight deck experience requirements. Usually a pilot will be considered inexperienced until X-number of hours/sectors in their respective seat, and there will be a prohibition on inexperienced pilots flying together. In my operation a * after the name denotes inexperienced. Unless specific in-seat training is carried out, a captain is prohibited from flying as an FO in the right seat. A new captain will fly a certain number of training sectors with a training captain in the RHS, then take a line check before being allowed on the line with a * next to their name.
Last edited by rudestuff; 11th May 2022 at 17:31.