By 1991, the airline was established as a key player in the regional market, utilizing a fleet primarily composed of Boeing aircraft. A significant milestone in the airline's expansion occurred in 1997 when it broke its domestic-only restriction to launch its first international services. This period saw the airline aggressively modernizing its fleet with the B767-300 arriving in 1994 and the Boeing 737-300 in 1997, to serve growing demand across East Asia.

Shanghai Airlines took delivery of its first Boeing 737-800 on 28 December 2001.

The arrival of the Next-Generation 737 allowed the airline to improve fuel efficiency, extend route flexibility, and enhance passenger comfort. The airline started deploying them primarily on high-demand domestic routes across China while gradually expanding into short- to medium-haul regional services.

The turn of the millennium brought a pursuit of capital and prestige. In late 2002, Shanghai Airlines was successfully listed on the Shanghai Stock Exchange. During the mid-2000s, the airline expanded its reach into the cargo sector with the founding of a dedicated cargo subsidiary in 2006. This era also marked the airline's entry into the global stage of airline alliances. On December 12, 2007, Shanghai Airlines was officially welcomed as the 19th member of the Star Alliance.

However, the most significant shift in the airline's history began in June 2009 when it was announced that Shanghai Airlines would merge with its cross-town rival, China Eastern Airlines. The merger was officially completed in February 2010, resulting in Shanghai Airlines becoming a wholly owned subsidiary of China Eastern. As a direct consequence of this consolidation, the airline had to terminate its membership with the Star Alliance on October 31, 2010. Shortly thereafter, in 2011, Shanghai Airlines followed its parent company into the SkyTeam alliance as an affiliate member.

Previously, the airline had received its first Airbus A321 on 28 July 2009, during a period of rapid fleet expansion, However, this addition was short-lived under the Shanghai Airlines brand, as the airline was merged into China Eastern Airlines. As part of the integration process, the newly delivered A321 aircraft was subsequently transferred to China Eastern Airlines.

Between 2011 and 2016, the airline underwent a period of fleet renewal and integration. It began retiring its older Boeing 757 and 767 aircraft in favour of more efficient models. Although it functioned as a subsidiary, it retained its distinct brand identity and its iconic "white crane" logo on a red tail. By March 2013, the airline began integrating Airbus A330 wide-body aircraft into its operations, often utilizing them on behalf of China Eastern for long-haul sectors to destinations like Melbourne, Australia. 

In 2014, Shanghai Airlines continued to refine its route network by increasing frequencies on key business routes and launching new connections in China. The airline also expanded select regional international services within East Asia, including routes to Japan and South Korea.

Fleet development remained a central theme through 2015, as Shanghai Airlines took delivery of additional Boeing 737-800 aircraft featuring Winglets for additional fuel savings, gradually replacing older models and improving operational efficiency. The newer aircraft featured updated cabin interiors, including improved seating and in-flight amenities, aligning the passenger experience more closely with China Eastern’s standards.

By 2016, Shanghai Airlines was operating an extensive domestic network supplemented by a growing number of regional international routes. Shanghai Airlines placed an order for the Boeing 787 Dreamliner when parent company China Eastern Airlines Group finalized the deal on April 27, 2016, as part of a broader widebody acquisition plan.

The agreement included Boeing 787-9 aircraft intended to support network expansion and improve fuel efficiency across intercontinental routes operated by both China Eastern and its subsidiary Shanghai Airlines.

In 2017, Shanghai Airlines further solidified its role within the China Eastern ecosystem, continuing to expand frequencies on high-demand domestic corridors while selectively adding new regional routes. The airline’s fleet remained focused on the Boeing 737 family, with additional 737-800 deliveries ensuring a relatively young and efficient narrowbody fleet.