The results are in. In October, for the first time in months, Boeing (NYSE:BA) beat Airbus (OTC:EADSY) in the race to sell the most planes in a calendar month.

At long last, Boeing beat Airbus in October. Has a new day dawned for the Seattle plane maker? Image source: Boeing.

The horse race
Late last week, we updated you on Boeing's airplane sales for the first full month of fall. For a change, Boeing didn't "fall" short. The Seattle planemaker added nearly five dozen new planes to its order book last month, which now stands at 566 gross plane orders, or 489 net of cancellations.

Airbus, in contrast, took in barely half as many October orders as Boeing did -- just 35 new planes tacked onto its tally. Airbus entered October with a commanding lead over its rival, however, having outsold Boeing nearly 2 to 1 through September. As a result, despite lagging behind its rival last month, Airbus has won 850 net new orders year to date.

The details
We'll discuss how Airbus has been thrashing its rival this year in a bit, but first, the obligatory details on Airbus' month that was. On Friday, Airbus released a report describing firm orders for the month of October. These included:

  • One A321 neo ordered by California-based Aviation Capital Group (which is, according to S&P Capital IQ, a subsidiary of privately owned Pacific Life Insurance Company).
  • four A350-900s going to Singapore Airlines.
  • 30 A330-300s bought by Chinese airplane lessor China Aviation Supplies Holding Company.

That's 35 planes, total. Year to date, this means Airbus' order book now looks like this:

  • 777 single-aisle "A320 Family" jets (which actually includes an A318, two A319s, and 222 A321s).
  • 119 widebody A330s, which compete with Boeing's 767, 777, and 787.
  • 14 A350 widebodies.

Airbus lost not a single plane order to cancellation in October, leaving it with still just 60 cancellations for the year. (Boeing has suffered 77 cancellations -- and out of a much smaller initial base of gross orders.) Subtract Airbus' 60 cancellations from its 910 gross orders, and its net plane orders come to the aforementioned 850 planes -- 74% more than Boeing can boast.

Where is Airbus beating Boeing?
Despite lagging in October, Airbus retains a commanding lead over its rival. But how? It really comes down to just one plane -- or rather, one plane, and one family of rivals to it.

So far this year, both Boeing and Airbus have sold roughly equal numbers of ultra-long-range "widebodies." Gross orders of Boeing 747s, 777s, and 787s, three planes of similar wingspan, total 137, versus Airbus orders for 133 A330s and A350s. Boeing also has orders for four dozen smaller, shorter-range 767 widebodies, however. Factor those into the mix, and there's an argument that Boeing leads Airbus in the market for "widebodies" as a whole.

Where Airbus really breaks away from its rival, though, is in the market for smaller, regional, single-aisle jets. The 777 "A320 Family" aircraft ordered from Airbus this year outnumber Boeing's best-selling 737 orders (381 of them) by more than 2 to 1.

Why is Airbus beating Boeing?
The reason for Airbus' sizable outperformance of Boeing on single-aisle jetliner sales isn't immediately obvious. Fuel efficiency probably plays a role. Also, Airbus' best-selling A320neo jet lists for just $106.2 million, or 3.5% cheaper than Boeing's analogous 737 MAX 8.

On the other hand, Airbus' second-best seller, the A321neo, costs $124.4 million -- 6.7% more than the Boeing 737 MAX 9. True, commenters on civil aviation website argue that the A321 is simply a better plane than the "underpowered and inferior" MAX 9. But that's a subjective opinion. Here's an objective fact:

Over the past year, the euro has lost about 15% of its value relative to the U.S. dollar.

Euro to US Dollar Exchange Rate Chart

Euro to U.S. Dollar Exchange Rate data by YCharts.

With both A320 and 737 aircraft priced internationally in dollars, you might think exchange rates are a non-issue. But in fact, the weakening euro means Airbus' costs for parts and labor in building its A320s are going down, while Boeing's are going up -- each relative to the other. This gives Airbus added wiggle room to sell its aircraft at cheaper-than-list prices, winning sales and stealing market share from Boeing, while still maintaining (and indeed growing) its own profit margins.

So yes, Boeing beat Airbus in October. But over the long run, this is still Airbus' race to lose. As long as exchange rates work in its favor, expect Airbus to outsell Boeing in the all-important single-aisle plane market.

As the euro plunged, Airbus sales took off in 2015. Image source: Airbus.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.