On opening day of the 2017 Paris Air Show, Boeing's (BA -2.66%) new 737 MAX 10 jet garnered most of the press attention. As expected, Boeing launched the latest member of its workhorse 737 jet family on Monday morning, announcing that it had already received 240 orders and commitments for the new jet.

The successful 737 MAX 10 launch was important for Boeing, as the company is trying to prevent Airbus from monopolizing the market for large narrowbodies. That said, Boeing entered the week with more than 4,400 unfilled orders for the 737 family -- enough to keep the production lines running for seven years.

By contrast, widebody orders have been harder to come by in recent years. Thus, the most important announcements of the day (from a business perspective) may have been Boeing's deals to sell 38 Dreamliners to a pair of aircraft leasing companies: AerCap (AER -1.09%) and CDB Aviation Lease Finance.

787 sales have been slow

Boeing's Dreamliner racked up a huge number of orders in the first few years after it launched. But since 2008, sales have been slow for the most part. During this period, Boeing has only surpassed 100 net orders for the 787 family in one year (2013).

A Boeing 787

Dreamliner order activity has been sluggish for the past few years. Image source: Boeing.

Until recently, Boeing wasn't concerned about this slow sales pace. The 787 family had such a long backlog that the order slump could be blamed on a lack of near-term product availability. It was assumed that sales would pick up once the backlog receded to a more normal level.

However, after three straight years with fewer orders than deliveries, Boeing ended May with 670 unfilled orders for the 787 family. That represents less than five years of production at the current build rate of 12 per month. The current backlog looks especially inadequate given that Boeing hopes to increase the production rate to 14 per month near the end of the decade.

Two new Dreamliner orders come in

On Monday morning, Boeing secured some much-needed Dreamliner orders. Most notably, aircraft leasing giant AerCap -- already the largest customer for the 787 family -- ordered another 30 787-9s. AerCap already owns 55 Dreamliners, and it now has 67 on order, including aircraft acquired through sale-leaseback deals.

Boeing also signed a memorandum of understanding for eight 787-9s with CDB Aviation, the Irish aircraft leasing unit of China Development Bank.

These deals with AerCap and CDB Aviation highlight the continued popularity of the 787-9 in the aircraft leasing world. This is important for its long-term success because aircraft leasing companies can make the Dreamliner available at a reasonable price to airlines that can't afford to buy one outright -- including young, fast-growing carriers that could become major Dreamliner operators in the future.

A good start, but there's more work to be done

Boeing netted 23 Dreamliner orders during the first five months of 2017. The AerCap deal brings its full-year firm order total for the 787 family up to 53. Including the commitment from CDB Aviation and a commitment from Singapore Airlines announced in February -- both of which are likely to be finalized later this year -- Boeing has signed deals for 80 787s year to date.

This is a good start, considering that many airlines are still holding off on widebody orders in light of the low fuel price environment. However, Boeing would need to sell at least 60 additional Dreamliners this year just to match the number of expected deliveries. It would need to sell even more to start building up the 787 family order backlog again.

As a result, investors should keep an eye on Boeing's order activity in the coming days at the Paris Air Show. Boeing needs to bring in more Dreamliner orders this week to maintain a realistic hope of increasing 787 production a couple of years down the road.