CDO = continuous duty overnight. Each airline calls them differently and I've had flight attendants flip out saying "THEY ARE CALLED STAND UPS!" Some places call them high speeds. Some places Stand Ups (Which I never understood).

Basically picture it as an overnight "sit" where you go to the hotel. You usually fly the last leg out to an outstation then the first leg back in the morning which would normally not allow legal rest. So you are on duty the whole time.

Pros: You do not start until usually pretty late - 8 or 9pm. You are also usually done pretty early, 5 or 6am. If you do a line of them, you usually only fly 20-30 hours a month but get what ever your line credit is.

Cons: Even best case scenario, you will get 4-6 hours at hotel which results in say 3-5 hours sleep. If our outbound leg is delayed (ie due to deicing, etc) your return leg will not be adjusted so the time you spend at the hotel will decrease (because you have no minimum rest time).

With that said, CDOs probably depend greatly on the way the contract language at each carrier is written. At Envoy they usually go pretty senior on the pilot side. On reserve they always go to the top reserve people - especially the way they work with our reserve rules. While some people say they just can not due CDOs, they never are forced on a person who doesnt want to do one since there are always people who would rather do them. They work great for local guys and even commuters on reserve (get one day 1 and one second to last day).