Like many major carriers around the world, theBoeing 737 series plays a key role in United Airlines’ day-to-day operations. When it comes to the next-generation 737 MAX family, according to data from ch-aviation, United flies both the MAX 8 and the MAX 9 variants, with 123 and 146 examples in its fleet respectively. Going forward, the carrier plans to increase its MAX 9 sub-fleet by more than 50%, with outstanding orders for 77 more jets.