How Does The Boeing 737-900ER Differ From Its Standard Counterpart?

The Boeing 737-900 was the largest variant of the US-based manufacturer's 737 Next Generation family, but some carriers were looking for an airliner that was even more capable. Ever since Boeing discontinued the 757 program back in 2004, the manufacturer had a problematic gap in its lineup and, even worse, a rival Airbus product, the A321, that was quickly taking over the top of the narrowbody market.