Over the past few years, Boeing (NYSE:BA) and Airbus have experienced a slump in wide-body orders, even as airlines have continued to buy narrow-bodies like the 737 and A320 at a frenetic pace. This downshift in order activity caused Boeing's backlog for models like the 747 and 777 to erode, forcing the aerospace giant to slash production of those models.

This article originally appeared in the Motley Fool.

Demand for passenger variants of the 747 and the current-generation 777 has slowed to a crawl. With fuel prices on the rise again, airlines are understandably tilting toward more fuel-efficient models, like Boeing's own 787 Dreamliner family.

However, cargo airlines are starting to pick up the slack. At this week's Farnborough Airshow, Boeing announced several orders for 747 and 777 freighters, helping it rebuild those aircraft families' order backlogs.

The cargo market is bouncing back

Prior to 2017, the air cargo market was under pressure due to a combination of slow demand growth (driven by economic slowdowns in some key emerging markets) and excess capacity (driven by belly cargo space on passenger aircraft flying new long-haul routes).

However, falling airfares and rising oil prices have caused global airlines to pull back on growth. Meanwhile, demand rebounded last year due to a strengthening global economy. Air cargo volume surged 9% in 2017, up from just 3.6% growth in 2016, according to the International Air Transport Association.

This improved supply-demand balance is finally driving a long-awaited recovery in the market for dedicated freighters. Boeing has been capitalizing on this rebound. For example, in the first half of 2018, it captured an order for 14 747-8Fs and four 767-300Fs from United Parcel Service and a deal for 12 767-300Fs and 12 777Fs from FedEx.

Boeing continues its freighter momentum at Farnborough

During the first two days of the Farnborough Airshow, Boeing announced three more freighter deals covering the 747-8F and 777F models. First, Qatar Airways firmed up an order for five 777Fs that had first been announced as a commitment a few months ago.

Second, Boeing announced a firm order and commitment from DHL for 14 777Fs, with purchase rights for another seven. The first four deliveries are scheduled for 2019. Boeing stated that it previously added some of these orders to its backlog without identifying the customer. (This likely refers to an order for 10 777Fs booked by Boeing last month and attributed to an unidentified customer.) The remaining firm orders will be added to the backlog at a later date.

Third, Russian cargo specialist Volga-Dnepr Group confirmed an order for five 747-8Fs and signed a letter of intent (LOI) for 29 777Fs. If the latter deal is firmed up, it would be the largest order for current-generation 777s since 2011. That said, Volga-Dnepr announced a "commitment" for 20 747-8Fs in 2015 and an "agreement" for the same 20 aircraft in 2016, but most of those orders were never firmed up. Thus, it's wise to take the new LOI with a grain of salt.

Filling in the order gaps

As of the end of June, Boeing had 23 unfilled orders for 747s and 101 unfilled orders for current-generation 777s. The deals announced at Farnborough will add to those totals, ensuring that the 747 line will keep running well into the 2020s and protecting the 777 line from further cuts.

Boeing still doesn't have enough 747 or 777 firm orders to contemplate returning to the higher production rates in place just a few years ago. But at least it's finally seeing some order momentum, which could pave the way for an eventual return to higher production of the 777 family — if not the 747 — a few years down the road.

Adam Levine-Weinberg has no position in any of the stocks mentioned. The Motley Fool recommends FDX. The Motley Fool has a disclosure policy.