Do airline transport pilot (ATP) trainees ever fly an empty aircraft? Consider the example where a pilot is under training to operate a 777. Would the pilot ever fly the real aircraft without any passengers? Or is training only limited to simulation?
When pilots are trained for flying in an aircraft type they have not flown in before, they go through type rating, then line training. During the type rating, they learn where all the instruments and buttons are, what starts which system, how the plane behaves, how to land and auto-land etc.
During line training, they spend time in the cockpit together with an instructor pilot, usually a senior captain. Most airlines have a 3-person crew in the cockpit when a new F/O is receiving line training. This training is about the airline specific bit of flying, company procedures etc.
Note that before going to type rating, the pilot already has at least a commercial flying license: they can fly already. Depending on the country, the type rating can take place in a Level D simulator for 100%. Some countries still require a couple of actual flights in an aircraft, but there is an increasing trend to use Level D simulators only, for two reasons:
- Back when the airlines paid and arranged for type ratings, it was relatively simple for them to arrange for an aircraft for a training flight, empty or not. But now a majority of type ratings is self funded, how does a student find the finance to charter an empty aircraft?
- The realism of Level D simulators is incredible. My office used to be not far from the simulators - every once in a while I would hear the siren for the sim coming down at an unscheduled time, for an unscheduled break: the stress level inside is real, you reckon that you are really 30,000 feet up with an engine on fire, alarms sounding, actual (non-toxic) smoke entering the cockpit, etc. After clearing the emergency, some students needed time to reflect.
Boeing predicts that we need 30,000 new pilots every year for the next 20 years. How do we streamline it such that all competent persons can become pilots, not only people with enough money to charter a plane?
As @user71659 points out, at airlines that only fly widebodies, standard entry position is a second officer/relief first officer/cruise pilot on a long haul plane like the 777. (Cathay Pacific, Singapore Airlines, Emirates, for example).
The answer depends on which country you are in. Under FAA regulations (and those countries that generally follow FAA rules), there is no requirement for you to actually fly the actual aircraft before taking passengers on a trip.
Under EU/EASA regulations, there is a default requirement, which is flown on a aircraft with instructors and fellow student pilots. This is called "base training".
AMC2 ORA.ATO.125(k)(1) states
With the exception of courses approved for ZFTT, certain training exercises normally involving take-off and landing in various configurations should be completed in the aeroplane rather than an FFS. For MPAs where the student pilot has more than 500 hours of MPA experience in aeroplanes of similar size and performance, these should include at least four landings of which at least one should be a full-stop landing, unless otherwise specified in the OSD established in accordance with Regulation (EC) 1702/2003, when available. In all other cases the student should complete at least six landings.
European airlines want to follow the US model since the actual flight time is expensive, hence the Zero Flight Time Training. If the specific airline has a ZFTT approved course with a Level D full flight simulator, a pilot with at least 500 hours of multi-pilot aeroplane experience can skip the actual flight if their first four flights are also done under a specially approved program.
The other answers describe the use of simulators, and I don't dispute that.
But, earlier this year, there was a documentary by EasyJet, where they showed how their new pilots trained, and they had to go through a couple of touch and go in an empty aircraft before they started flying with passengers. So it likely depends on each airline's policies.
For a slightly less clear example, this post by Air Canada implies that the new B737MAX is being used for training this weekend.
All type rating training would be done in full motion simulators. The problem with doing it in the real thing is that it is prohibitively expensive. Also sims allow pilots to run through emergency scenarios - and sometimes allow them to fail and crash - in order to teach key points and reinforce training. Large commercial airplanes are rarely flown empty; the only examples I can think of are test flights after maintenance has been performed or on ferry flights to a departure city. When I interned at Boeing as an engineer in 2000, the only empty flights once the airplane was purchased were short ferry hops. One airline bought a 777-200, thence flew it form KPAE 50 nm south to KSEA, where, within an hour, it was fully fueled, catered, loaded with passengers and flight crew and departed on a polar flight to Moscow, Russia.