Some applications for retreaded tires are airplanes, racing cars, buses and delivery trucks. Additionally, they make retreaded tyres for aircraft. Marie Louise worked as a domestic worker and Ernest retreaded tires. Tires that are fully worn can be retreaded, re-manufactured to replace the worn tread. About 90% of the original tires by weight is retained in retreaded tires. A worn tire can often be retreaded. Tires can be retreaded multiple times if the casing is in usable condition. About 17.6 million retreaded tires were sold in North America in 2006. Some tires may also be retreaded for re-use. Material cost for a retreaded tire is about 20% that of making a new tire.