most airline crews start the day and work the entire day as a 'crew' which includes everything from arriving at the aircraft to generally leaving the plane at the end of the day together. there is no way in hell i would even start boarding a flight without seeing if we even had pilots (crew always look for a good reason to cancel the flight and go home.. lack of tech crew is a big one haha)
tell your friend its impossible. this industry is not only highly regulated, but built on a big communication platform which is put in place to prevent accidents. perhaps on a train, crew could get on and not need to know there is a driver or not.. a plane is a different story. The tech crew are part of the crew and we do communicate alot. there is no way in hell this is remotely possible.