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.
Lego operates 132 so-called "Lego Store" retail shops. There are stores at the Downtown Disney shopping complexes at Disneyland and Walt Disney World Resorts as well as in Mall of America in Bloomington, Minnesota. The opening of each store is celebrated with weekend-long event in which a Master Model Builder creates, with the help of volunteers—most of whom are children—a larger-than-life Lego statue, which is then displayed at the new store for several weeks.
City has had many games since it was released. One in particular, The Robot Chronicles, was a cross-over game which saw the City, Racers, and Agents 2.0 all together in Lego City, where the player controlled and unlocked vehicles in each theme to play through a campaign. This campaign/game was also tied into a My LEGO Network The Robot Chronicles campaign- playing the game earned rewards in MLN which could be used in that campaign to eventually get the Key to LEGO City.
The final two minifigures are the Biplane Pilot and the intrepid Wing Walker. Both of these minifigures share the same white torso which is printed with a flight suit design overlaid with dark red and bright light orange flames plus a logo over the left breast. The torso design is superb and it can at present only be found in this set. Both minifigures are provided with a reddish brown aviator cap and dark bluish grey goggles, and the pilot (below left) also gets an alternative to this headgear in the form of medium dark flesh mid-length hair which has only ever appeared in five sets in this colour.