Since the 1950s, the Lego Group has released thousands of sets with a variety of themes, including space, robots, pirates, trains, Vikings, castle, dinosaurs, undersea exploration, and wild west. Some of the classic themes that continue to the present day include Lego City (a line of sets depicting city life introduced in 1973) and Lego Technic (a line aimed at emulating complex machinery, introduced in 1977).
Billund Airport (Danish: Billund Lufthavn) (IATA: BLL, ICAO: EKBI) is an airport in Denmark. Located 1 nautical mile (1.9 km; 1.2 mi) northeast of Billund, it serves as one of the country's busiest air cargo centres, as well as a charter airline destination, although some regular airlines also offer flights there. Nearby Legoland Billund park is the largest tourist attraction in Denmark outside Copenhagen.
Since 1963, Lego pieces have been manufactured from a strong, resilient plastic known as acrylonitrile butadiene styrene (ABS). As of September 2008, Lego engineers use the NX CAD/CAM/CAE PLM software suite to model the elements. The software allows the parts to be optimised by way of mould flow and stress analysis. Prototype moulds are sometimes built before the design is committed to mass production. The ABS plastic is heated to 232 °C (450 °F) until it reaches a dough-like consistency. It is then injected into the moulds at pressures between 25 and 150 tonnes, and takes approximately 15 seconds to cool. The moulds are permitted a tolerance of up to twenty micrometres, to ensure the bricks remain connected. Human inspectors check the output of the moulds, to eliminate significant variations in colour or thickness. According to the Lego Group, about eighteen bricks out of every million fail to meet the standard required. Lego factories recycle all but about 1 percent of their plastic waste from the manufacturing process. If the plastic cannot be re-used in Lego bricks, it is processed and sold on to industries that can make use of it. Lego has a self-imposed 2030 deadline to find a more eco-friendly alternative to the ABS plastic it currently uses in its bricks.
Since around 2000, the Lego Group has been promoting "Lego Serious Play", a form of business consultancy fostering creative thinking, in which team members build metaphors of their organizational identities and experiences using Lego bricks. Participants work through imaginary scenarios using visual three-dimensional Lego constructions, imaginatively exploring possibilities in a serious form of play.