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.

As a result, United Airlines has become the first airline to operate a fleet of 1,000 aircraft. ... according to Aerolopa, United Airlines' Boeing 737-800 operates services in Guam and Micronesia.

But when the dyed-in-the-wool, 100% Boeing customer United switched over to the A320, that's when they panicked and decided they needed to update the 737." The first NG variant — the 737-800 ...