When Falcon Heavy lifts off, it will be the most powerful operational rocket in the world by a factor of two, with the ability to lift into orbit nearly 64 metric tons (141,000 lb) - a mass greater than a 737 jetliner loaded with passengers, crew, luggage and fuel, according to SpaceX's official website. 

"Falcon Heavy's first stage is composed of three Falcon 9 nine-engine cores whose 27 Merlin engines together generate more than 5 million pounds of thrust at liftoff, equal to approximately eighteen 747 aircraft. Only the Saturn V moon rocket, last flown in 1973, delivered more payload to orbit," the website further mentions.