Boeing and Spirit AeroSystems, a subassembly provider to Boeing 737 and other commercial programs, are practicing for a narrowbody production rate of 57 aircraft a month in Wichita, Kansas.

Spirit’s fabrication unit already is getting into rate 57 production, according to Spirit president and CEO Tom Gentile. But the rehearsals—which were Boeing’s idea—are across the board and have helped identify needed changes before Boeing officially declares the rate increase, starting with a need for additional dollies to shuttle parts around Spirit’s factory.

“With the rehearsals, we practice three deliveries every day for three days in a row,” Gentile told the Cowen and Co. Aerospace and Defense Industrials Conference Feb. 7.

“So, [we] stress the system, and then we relax back to the normal pattern to see where we need to make improvements,” Gentile said. “We check on labor productivity, we check on tooling, we check on the infrastructure. We’ve identified some gaps and opportunities to improve.”

The rehearsals for rate 57 come after Spirit and other suppliers fell behind in 737-related deliveries to Boeing in 2018, spurring a sizable response from both companies that included a surge in hiring, some of which is being retained for the hike to 57.

“We’re well on the way to implementing the 57 for 737,” Gentile reiterated at the investor conference.

Cranking up to rate 57 further helps Spirit be more efficient now and prepare for further rate hikes, the CEO explained. In 2016 at rate 42, Spirit had two production lines in its main plant, each producing 21 per month, or essentially one unit from each line every work day. For rate 47, Spirit opened a third line, but only one aircraft unit came off every four days there.

At rate 57, Spirit will have three lines each producing 19 737 subassemblies a month, or about one a day each and with a two-day buffer built in to each line.

“We’re going to be very balanced—more balanced than we’ve been since 2016,” Gentile said. “If they go to 63, we could increase those 19 units-per-month lines, the three of them, to 21, which is where we were in 2016.”

The rehearsals come as Boeing and Spirit appear to be working closer than at any time since Spirit spun out of Boeing in 2005. The tighter relationship stems in part from a new master agreement the companies definitized in January. Under that arrangement, the companies agreed to split the cost of many improvement efforts.

“With skin in the game on both parties, there is an incentive,” Gentile said. “You can’t be one-sided, or you will never get that support from engineering.”

Of course, the ultimate reward is cashing in on the roughly seven-year backlog of 737 orders. For Spirit, analysts at Jefferies have estimated that each aircraft increase to the monthly 737 production rate could be worth $76 million, or one percentage point of growth of revenue, and $0.10 of additional earnings per share.

Spirit also sees an opportunity for growing work with Airbus, too, starting with the new A220. Gentile noted that Airbus has said it wants to cut costs in the supply chain to help justify taking over the former CSeries from Bombardier. Spirit already provides the pylon on the aircraft, but nothing else. With the program handover, Airbus has more authority to move work among suppliers.

“There is a big opportunity for us to get more work packages on the A220 to help out on Airbus’s cost challenges,” Gentile said.

Michael Bruno,