Boeing and Turkish Airlines confirm an order for 15 next-generation 737s. Photo: Boeing. 

On Wednesday, Boeing (BA 2.98%) announced that SunExpress, a Turkish carrier, had completed an order for 15 737 MAX 8s and 25 next-generation 737-800 planes. Further, Boeing stated, "The order, valued at more than $3.8 billion at list prices, also includes options for 10 additional 737 MAX 8s." Even better? The order is the largest in Sun Express' history and brings the total number of 737 MAX orders to almost 1,800. Here's what else you need to know.

Boeing's 737
According to Boeing, the 737 Max is designed for maximum efficiency, maximum reliability, and maximum passenger appeal. Further, it's part of Boeing's newest family of single-aisle planes, expands on the 737's next-generation line, and, as it's a part of the 737 family, is one of Boeing's most popular commercial planes .

However, that doesn't mean the 737 family is without competition. European Aeronautical Defense and Space's (EADSY 0.57%) Airbus A320 line is a direct competitor to the 737, and when it comes to sales, both Boeing and Airbus aren't shy about touting their plane as better than the other. In fact, on it's official 737 Family page, Boeing states, "the 737s will have on average 590 fewer delays and therefore avoid disrupting 65,000 fewer passengers when compared to a fleet of A320s." 

As such, when one of these companies scores a major contract win over the other, it's cause for celebration -- and perhaps just a bit of gloating.

What to watch
Boeing's 737 family is extremely important to Boeing's bottom line. Not only is it incredibly popular when it comes to sales, but when it comes to future airplanes sales, single-aisle planes are expected to play a growing role. This is especially true for major markets like the Asia-Pacific region. Both Boeing and Airbus have valued this market at well over $1 trillion for the next 20 years, and agree that demand will be highest for single-aisle airplanes. Consequently, investors would do well to keep close tabs on Boeing's 737 sales, as well as actual deliveries.