Group 1 - The article discusses the manufacturing process of aircraft skin, highlighting its critical role as the outer shell of the aircraft, which requires high strength, precision, and low weight [4][5]. - The thickness of the aircraft skin typically ranges from 3mm to 6mm, with the thinnest parts being just over 1mm [4]. - The company has invested 138 million yuan to introduce mirror milling technology, establishing the largest mirror milling production line cluster in China, which enhances precision to 0.1mm [5][6]. Group 2 - The mirror milling process allows for simultaneous machining on both sides of the skin, significantly improving precision and reducing production time compared to traditional chemical milling [5]. - A precision improvement of 0.2mm can lead to a weight difference of over 100 kilograms for an entire aircraft, which is significant given the importance of weight in aircraft design [5][6]. - The company has successfully delivered its first domestic aircraft skin, meeting the production needs for the C919 aircraft, indicating a shift towards domestic manufacturing capabilities in the aerospace sector [6].