Entering 2017, most pundits expected a meaningful slump in aircraft orders, following years of record order activity early in this decade. Even top airplane manufacturers Boeing (BA -1.91%) and Airbus (EADSY 1.22%) had moderate expectations.

However, 2017 hasn't turned out quite as expected. Boeing is on pace to have an extremely good year in terms of aircraft orders. If Airbus can firm up a big commitment it landed last month by year-end, its 2017 performance won't look too shabby, either.

So far, Boeing is the big winner of 2017

Last year, Boeing's order activity fell short of its delivery total for the first time since 2009. (The company received 668 net firm aircraft orders, compared to 748 deliveries). By contrast, Airbus continued sailing along, capturing 731 net firm orders while delivering 688 aircraft.

An Airbus A320neo aircraft on the ground.

Airbus has routinely led Boeing in terms of orders in recent years. Image source: Airbus.

In 2017, Boeing has been in the lead all along. It started the year strong, and the launch of the 737 MAX 10 at the Paris Air Show in June gave it even more momentum. By early November, Boeing was already approaching its 2016 order total with more than 600 net firm orders. As of Dec. 7, it had 661 net firm orders for the year, having finalized a 75-airplane deal with prominent aircraft lessor Avolon in mid-November.

Meanwhile, Airbus has fallen on tough times (somewhat) this year. As of the end of November, it had only booked 333 net firm orders in 2017. As a result, it is on pace for the worst sales year for either of the two aircraft manufacturing giants since 2009.

December is usually a big month

One year of slow sales would hardly be devastating for Airbus. The company still ended last month with more than 6,600 firm orders in its backlog, putting it more than 900 units ahead of Boeing in the overall order race.

However, 2017 may turn out a lot better for Airbus than its 11-month order total would suggest. Boeing and Airbus both routinely bring in a disproportionate number of their orders in December, as their sales teams race to nail down as many orders as possible before year-end. For example, in 2016, Boeing finalized around 200 orders just in the last week and a half of the year.

A rendering of the Boeing 737 MAX 8 jet.

30% of Boeing's 2016 orders came in the last week and a half of the year. Image source: Boeing.

At last month's Dubai Airshow, Airbus received its largest aircraft commitment ever. Investment firm Indigo Partners -- which owns stakes in several ultra-low cost carriers across the world, including Frontier Airlines -- plans to buy 430 A320neo family planes. If Airbus can firm up this one order in December, it would flip the script for the year, vaulting past 750 net orders.

Boeing is also looking to finish 2017 on a high note. In the past few months, it has received commitments from Turkish Airlines and Emirates to buy 40 787 Dreamliners each. It also has hundreds of outstanding commitments from the Paris Air Show, mainly covering 737 family jets, along with various other agreements announced in the past year or two.

If Boeing has a typical December order performance, it could exceed 800 firm orders for 2017, which would surpass its projected deliveries for the year (760-765).

This could be a busy month

If the year ended today, Boeing could call it a success. It has already nearly equaled its 2016 order total, with a better mix of widebody aircraft (which carry higher price tags and have shorter backlogs than the popular 737 narrowbody jet).

Nevertheless, I expect Boeing to make a strong push to finalize as many of its outstanding aircraft deals as possible during December to support its plans to increase output on the 737 and 787 production lines.

Airbus has even more motivation to finish 2017 with a slew of orders. It would be somewhat embarrassing if it ended the year with only half as many orders as Boeing. Furthermore, the Airbus sales team is probably eager to show that it hasn't lost its mojo following the recent retirement of longtime sales chief John Leahy. As a result, investors should expect the year-end order totals for Boeing and Airbus to look a lot better than the current numbers.