Boeing (NYSE:BA) and Airbus (NASDAQOTH:EADSY) each announced hundreds of orders and commitments for commercial aircraft at last month's Farnborough Airshow. This seemed to mark the continuation of an uptick in order activity that began last year.

Yet when the time came for the two aerospace giants to report their July order totals, it became clear that very few new firm orders were placed during the air show. Indeed, July was one of the worst months of 2018 for aircraft orders at both companies.

Boeing comes up almost empty

In the first half of 2018, Boeing booked 460 net firm orders for commercial aircraft. This was more than double Airbus' order total during the same period, and it put Boeing in good position to increase its backlog for a second consecutive year.

Boeing followed up this strong first-half performance by capturing more than 500 new firm orders and commitments at the Farnborough Airshow. Yet there were far more commitments than firm orders. Additionally, many of the firm orders that Boeing reported for the air show had previously been added to its order book (attributed to unidentified customers).

Indeed, Boeing booked firm orders for just 30 aircraft in July, offset by three cancellations. This left it with 487 net orders year to date. Boeing is still on track to have a very good year in 2018, but it has a lot of work left to finalize its hundreds of outstanding commitments by year-end.

A rendering of a Boeing 737 MAX 8

Boeing didn't finalize very many orders last month. Image source: Boeing.

July was an even slower month for Airbus

If Boeing's July order activity seemed underwhelming relative to the announcements it made at the Farnborough Airshow, Airbus' performance was even worse. The European aircraft manufacturer booked just one firm order last month: a deal for eight A350-900s from an undisclosed customer. This brought its year-to-date net firm order total to 214 aircraft.

Airbus' July order update indicates that several deals it had previously described as "firm" had not been 100% finalized by the end of the month. (At the end of the Farnborough Airshow, Airbus reported that it had captured 354 firm orders year to date.)

A highly touted deal to sell 60 A220-300s to JetBlue Airways appears to have been one of these not-quite-firm orders. Airbus will almost certainly be able to finalize the JetBlue deal and the other orders it described as "firm" in the post-Farnborough press release during 2018, but that would still leave it well behind Boeing in the annual order race.

In fact, Airbus will need to convert all of the 338 commitments it received at the Farnborough Airshow -- and then some -- into firm orders over the next five months just to match its projected 2018 production of about 800 aircraft.

Production is also a big question mark

The large number of commitments that haven't been converted into firm orders isn't the only major problem facing Boeing and Airbus today. Both manufacturers are also struggling to meet their production targets due to wide-ranging supply chain problems.

Engine makers have had the hardest time meeting their quotas, largely because they have had to shift to new, more fuel-efficient designs while simultaneously increasing their total production. That said, there have been plenty of miscues elsewhere in the Boeing and Airbus supply chains.

Airbus has felt the biggest impact so far. That said, Boeing's output slowed dramatically in July, even though management stated just a few weeks ago that it didn't expect any delivery delays.

Unfortunately for Boeing and Airbus, the models that account for the vast majority of their recent orders (the 737 MAX and A320neo families) are facing the biggest production shortfalls. Investors need to hope for either a quick resolution to these long-running supply chain problems or an order turnaround for slower-selling models -- or better yet, both.

Adam Levine-Weinberg owns shares of JetBlue Airways and is long January 2019 $10 calls on JetBlue Airways. The Motley Fool recommends JetBlue Airways. The Motley Fool has a disclosure policy.