The Boeing 737 MAX 9 and Airbus A321neo are two of the largest narrowbody aircraft currently in service. The Boeing 737 MAX 9, measuring 138 ft 4 in (42.16 m) in length, is the biggest variant of the 737 MAX series available today, though it will be surpassed by the upcoming 737 MAX 10 once certified. It can accommodate up to 220 passengers but has not sold as well as its smaller counterpart, the MAX 8.
In contrast, the Airbus A321neo is part of Airbus's A320neo family and extends nearly seven meters longer than the A320neo. With a maximum capacity for 244 passengers, it usually seats between 180 and 220 in a two-class configuration. The A321neo measures a total length of 146 ft (44.51 m), making it almost eight feet longer than its Boeing competitor.
According to Avi Johnson from Shutterstock, "The Airbus A321neo is bigger than the Boeing 737 MAX 9 by almost eight feet in length and also has a wider fuselage." Despite this advantage in size, "the MAX 9 narrowly beats it in terms of wingspan and height," with dimensions listed at a wingspan of "117 ft 10 in (35.92 m)" compared to "117 ft 5 in (35.80 m)" for the A321neo.