It's time to revisit the MoM segment. Regular readers know this is one of our favorite subjects. Starting with two charts showing the number of single-aisle MoM in the fleet (left) and the percent of the fleet these aircraft account for (right). [caption id="attachment_90188" align="aligncenter" width="1917"] AirInsight[/caption] The number of aircraft is growing steadily, perhaps even rapidly. On the right, these aircraft are nearly 35% of the fleet. Since they are single-aisle, we can expect them to do several daily turns. The following table lists the daily A321 operations in the US as an example of the seat generation involved. [caption id="attachment_90192" align="aligncenter" width="640"] US DoT T2; AirInsight[/caption] When we break down the data into airlines, we see the following. [caption id="attachment_90189" align="aligncenter" width="1916"] AirInsight[/caption] The charts above include A321s, 757s and 737- 900s plus MAX 9s. Some points Alaska's jump is driven by its MAX 9 deliveries. Close to 70% of its fleet is MoM. Notice the sharp rise at Frontier. This is noteworthy, given the trouble at Spirit, which has also moved to the MoM. This segment may now be oversupplied in seats. United shows a blip at the end of the curve. That blip will grow this year as more A321s arrive. Summary The US was the largest market for the 757. It is expected to remain focused on aircraft of that size, and indeed, it appears. As 757s are retired from passenger service, Airbus and Boeing struggle to meet demand. A321 deliveries being slowed at JetBlue and Spirit are perfect for United to seize the opportunity. However, the absence of the MAX 10 has an impact. Several US airlines have big orders and would take them as quickly as possible. The MoM attraction is growing outside the US, too. India and China are big markets. So is the EU.