in the cockpit, the captain and first officer make their final preparations. >> okay. oxygen. check. instruments. check. >> in a 777 simulator, commercial pilot mitchell casado shows cnn the preflight prep. >> it's going into this system here. >> the pilot loads the route, programming the aircraft to fly to its destination. >> and it's essentially step-by-step going to take this plane from kuala lumpur all the way to beijing. >> the plane is ready. before taking off, paul weeks sends a message home. >> the last line was, this counts as one day, so that means it's only 27 days until i see you all again. >> around 12:30 a.m., malaysia airlines 370 pushes back from the gate and gently eases toward the runway. the aircraft is cleared for takeoff. >> let's go. >> yeah. all right. so the brakes are off. and everything is set.