United's second oldest 737-700 is N24702, a 27.1-year-old 737-700. This aircraft took its first flight on March 8, 1998, and was delivered to Continental on March 31, 1998.

Airlines like WestJet, La Compagnie, Icelandair, and SAS have also continued to rely on the deployment of aircraft like the Boeing 737 MAX and Airbus A321neo on transatlantic services.

United Airlines may not take delivery of the Boeing 737 MAX 10 until 2027 or 2028 because of uncertainty about when the plane will be approved for use, an executive for the carrier said Tuesday.

Boeing did not immediately comment. In 2017, United made a major order of the MAX 10, which is larger and can carry more passengers. The 737 is Boeing's top-selling airliner.