Tuesday was an important day at Boeing South Carolina.

In addition to producing 787 Dreamliners at an ever-increasing rate and preparing to resume deliveries after a nearly five-month drought, the North Charleston plant played host to the company’s annual investor conference.

Keen-eyed financial analysts toured the local factories before retiring to Kiawah for the rest of the event, which included presentations by Boeing’s top executives in town from Chicago and Seattle.

Even with all that going on, however, Jack Jones, the boss of the local plane-making complex, had something else on his mind. And he let his workforce know, in a Tuesday afternoon email titled “The IAM is back, and they want your money.”

That’s right. Jones wanted to talk union.

He had gotten wind that the International Association of Machinists & Aerospace Workers had “recently contacted some of you yet again trying to convince you to sign a union card or vote for union membership.”

“I want to be clear that it’s Boeing’s desire to remain union-free in South Carolina so we can keep the open culture of collaboration between teammates that we’re all working hard to build,” Jones wrote. “I firmly believe a union is not in your best interest, nor is it in the best interest of our company, our BSC site, our customers, nor our community.”

Over the course of some 660-odd words, Jones made his pitch explicitly and implicitly, alternatingly conciliatory and firm.

He praised what has been accomplished so far without a union and reminded his workforce of the expectation that things stay that way.

He noted Airbus’ decision to build a plant in Mobile, Ala., and the incentive package South Carolina swiftly approved last month to help finance Boeing’s next planned expansion. He did not mention what is also generally known: South Carolina is a right-to-work state, and its political leadership, particularly Gov. Nikki Haley, is generally anti-union.

Jones conceded “we’re still a new site and I realize we may get some things wrong and need to go back to fix them.” He didn’t specify further.

And he reminded workers that they have the right to speak to IAM members about signing up but that they also have the right to “respectfully request to be left alone.” He urged them to “read the fine print” and “consider your choices carefully.”

“Boeing is committed to and invested in South Carolina and our BSC teammates, but our success hinges on our ability to continue working together, directly, without a third party, to solve issues,” Jones wrote. “Let’s keep up the good work and prove to the world that we can continue to grow at BSC together as one team without the distraction that a union brings.”

Tommy Mayfield, the IAM Grand Lodge representative for the Southern territory, has seen the email and others like it. He said Boeing has also been delivering the message in regular “captive audience” group meetings at the plant.

“Boeing communicates regularly with its employees to make sure they’re informed on a wide variety of subjects,” company spokeswoman Candy Eslinger said in an email.

Mayfield said he’s been holding his own meetings and keeping in touch with interested Boeing South Carolina workers all the while.

“The thing with Jack, that’s fine,” Mayfield said when reached by phone Thursday, before clarifying Jones’ opening line. “But we haven’t left. We’ve always been here.”

As Boeing likes to point out, the IAM does have a history in North Charleston.

The union narrowly won representation rights at the complex’s aft-body factory in November 2007, back when it was owned by Vought Aircraft Industries, but was decertified in September 2009.

Then, of course, the Seattle-area Machinists claimed Boeing built the now 2-year-old North Charleston final assembly line in retaliation for past strikes in the Puget Sound, and the resulting National Labor Relations Board complaint hung over the local plant before the case was finally dismissed as part of a grand bargain in December 2011.

Still, the union issue has lingered in North Charleston, and Mayfield’s meetings drew the attention of news reporters last fall.

Speaking this week, Mayfield said he has continued to collect signed authorization cards for possible submission to the NLRB. He wouldn’t say how many he’s received but said there’s been a steady response, through the mail and in person.

“I received several cards yesterday,” Mayfield said, referring to an informational meeting he hosted at a North Charleston hotel.

To stage an election, Mayfield needs cards from at least 30 percent of the proposed bargaining unit, though the actual goal would be somewhere north of 50 percent. There are well over 6,000 people who work at Boeing South Carolina, but the unit would be a considerably smaller subset of that, including blue-collar mechanics and assemblers but excluding any contractors, managers and white-collar workers. Mayfield said employees’ concerns continue to range from fair opportunities for promotion to wages and overtime.

Working more than 40 hours per week has been a fact of life at Boeing South Carolina, but according to a person who works at the plant, management’s promise to curtail it has finally started to come true in the past month or so. A relief to some, that’s a blow to those who had come to rely on the extra pay.

“As we come down the learning curve and implement continuous production and process efficiencies, it’s just natural that the need for overtime across the site would decrease,” Eslinger, the company spokeswoman, wrote in an email.

Mayfield said the reduction in overtime would bring take-home pay down to an uncomfortably low level for some heads of household.

“They make low wages out there,” Mayfield said, “and unless they work the overtime they have a hard time, I think.”

Boeing is sensitive to this concern, and wages have been a subject of discussion in the group meetings at the plant. Jones alluded to the issue in his email.

“No union can guarantee pay raises and no union can guarantee job security,” he wrote. “Business success and winning in the marketplace drive job security.”

Mayfield conceded that truth but added, “I don’t know of any contract that I helped negotiate that the employees didn’t get some increase in wages.”

In October, Mayfield said there could be a vote “within a year,” and this week he reiterated that prediction, saying, “I would say so. That is my belief.”

It’s still hard to gauge how realistic Mayfield’s ambitions are, but with all that’s at stake, Jones isn’t taking any chances.

Reach Brendan Kearney at 937-5906 and follow him on Twitter at @kearneybrendan