The Boeing 737-900 and 737-900ER are the longest variants in the US manufacturer's 737NG ('Next Generation') series, clocking in at 42.11 meters in length. The latter version has sold very well, with more than 500 examples produced. However, the standard 737-900 performed poorly in this regard, with sales barely exceeding 50. Let's see who flies this rare variant of the 737 today.