Talk of trade protectionism this presidential season is having a chilling effect on U.S. aerospace companies looking to locate production south of the border.
For more than a decade, Mexico has aggressively pitched itself as a pro-business and lower-cost alternative for U.S. industrial companies seeking to relocate or expand. Canaccord Genuity estimates Mexican facilities allow some U.S. companies to achieve a labor savings of as much as 80 percent.
"Many U.S. suppliers have recently been moving aircraft parts production and assembly to Mexico as a way of lowering their cost base," Canaccord Genuity aerospace analyst Ken Herbert said in a recent research note. "The potential impact on U.S.-Mexico relations under a [Donald] Trump presidency are a material concern."
U.S. companies or their contractors with an industrial presence in Mexico include Fortune 500 names General Electric, Honeywell, Eaton, Textron, L-3 Communications and Rockwell Collins. Even major suppliers to aerospace giants Boeing and Europe's Airbus have operations in Mexico.
Privately held Icon Aircraft recently announced plans to open a composite air-frame components plant in Tijuana, Mexico, where it eventually expects to employ as many as 1,000 workers. The Vacaville, California-based manufacturer of the A5 light-sport aircraft plans to have the Mexico plant operational next month.
Still, experts say the influx of aerospace companies into Mexico has started to moderate and some blame the U.S. election.
"Right now they are a little bit on hold," said Isaias Rivera, marketing coordinator of American Industries Group in Guadalajara, Mexico.
American Industries Group assists U.S. companies establish manufacturing or distribution operations in Mexico. Rivera said potential customers are generally "not taking positions right now" out of fear the next U.S. president could change the 1994 North American Free Trade Agreement.
Indeed, Rivera said the firm postponed a Mexico business seminar it holds annually in the U.S. "because we were not having the response that we usually have. They are waiting for the elections to see what happens."
The automotive industry — another major industry with operations in Mexico — appears to holding up better.
"Aerospace has been decreasing compared to other years and auto has increased," said Rivera.
Trump, in remarks last month during the first debate with Democrat Hillary Clinton, called NAFTA "defective" and "one of the worst things that ever happened to the manufacturing industry." Clinton, meanwhile, has shied away from fully embracing NAFTA and has been critical of the Trans-Pacific Partnership and China, including need for "a trade prosecutor."
"While pushback on the Trans-Pacific Partnership could have some implications for aircraft sales into the Asia region, we do not view this as a significant risk," said Herbert. "Some speculate that the lack of the TPP could ultimately help Airbus gain share as the perception of Boeing is negatively impacted in the Asia region, but it is early to make this call."
Still, the supply chain situation presents vulnerabilities to the aerospace industry due to the extensive nearshoring, or manufacturing in Mexico for the U.S. market. Some of the companies with operations in Mexico warn about the risks in their annual 10-K filings with the Securities and Exchange Commission.
"A number of risks inherent in international operations could have a material adverse effect on our results of operations," TransDigm Group said, citing among other things currency fluctuations, trade policies and political uncertainties. The Cleveland-based company, which lists Boeing and Airbus as its two top customers, operates two industrial plants in Mexico.
According to Canaccord's Herbert, the relocation of manufacturing "is often done with the encouragement and direct support of Boeing." As an example, he estimates some commercial program suppliers such as TransDigm, Triumph Group, Esterline Technologies and Ducommun have production in Mexico that accounts for as much as 10 percent of total manufacturing capacity.
CNBC reached out to the suppliers for comment but they declined comment or didn't respond.
"While sales are typically in U.S. dollars, and each of these suppliers uses some hedging to limit the FX risk, the risk of incremental costs, or a deterioration of U.S.-Mexico trade relations are a concern," Herbert said.
Most of the American companies have facilities in aerospace and defense industry hubs where there's a growing labor force of engineers for everything from assembly work and manufacturing to repair, maintenance and design.
"In order to fully develop its A&D industry, the Mexican government paid attention to the talent management and established many research centers and institutions to serve the industry and enhance its current situation in the A&D industry," PricewaterhouseCoopers' Mexico unit said in a report last year.
In all, about 300 foreign companies have operations in Mexico and more than three-fourths of them are American, according to PwC.
As of 2014, nearly 30 percent of the aerospace work was concentrated in the Mexican state of Baja California, where an aerospace forum is scheduled next week in Tijuana to promote the region's manufacturing prowess.
The Mexican central state of Queretaro is where GE has an advanced engineering center that employs 1,800 Mexican engineers to design products, solutions and software for aviation, power and other sectors. Another aerospace cluster is in the Mexican border state of Chihuahua, where Textron does work on airplanes and helicopters.