The Detroit auto show kicked off this week with a burst of hoopla and glam, including a Darius Rucker concert sponsored by Ford Motor and an indoor test track built by Jeep that features a hill with a 40-degree slope.

But beyond the excitement and bright lights, Detroit’s annual auto show has been clouded by foreboding and dread. The three established U.S. automakers, the anchors of the show, are locked in difficult contract negotiations with the labor union that represents nearly 150,000 of their employees.

Even as automakers sought to drum up excitement about new versions of popular vehicles like the Ford F-150 pickup truck and the GMC Acadia sport utility vehicle to journalists, analysts and dealers, labor negotiators were racing to avoid a strike by the United Auto Workers that could make it impossible for those new models to find their way to showrooms. Despite those efforts, the union called a strike at three factories starting Friday.

The three automakers based in the Detroit area — General Motors, Ford and Stellantis, which owns Jeep, Chrysler and Ram — are entangled in their greatest labor crisis in more than a decade even as they seek to display their best and brightest new models.

“You can feel it,” said Matt DeLorenzo, an independent auto analyst and author. “The executives I’ve talked to, you can see they’re concerned. I don’t see a lot of optimism that it’s going to be resolved fairly quickly.”

The U.A.W. and its new president, Shawn Fain, are seeking a 40 percent increase in wages over the next four years. The union has also demanded pension improvements, a shorter workweek, company-paid health care for retirees and an end to a wage system in which new hires start at about half the top union wage of $32 an hour.

The automakers, which have been making near-record profits for the last several years, have countered with wage increases about half of what the union is seeking, while rejecting most of the U.A.W.’s other demands.

There were few direct references to the U.A.W. talks at the show, which will open its doors to the general public on Saturday. But a prolonged strike would almost certainly jeopardize the automakers’ plans to roll out new cars and trucks to take advantage of still strong demand.

The auto industry has spent much of the last three years struggling to produce enough vehicles because of pandemic shutdowns and supply chain chaos. The inventory of new cars remains very low by historical standards, and prices are quite high, helping to raise profits.

If striking workers slow or stop production lines for many weeks or several months, customers looking for new cars will increasingly turn to foreign automakers or Tesla, the Texas-based producer of electric vehicles that is growing fast. Those other automakers operate U.S. plants that use nonunion workers and their production is unlikely to be affected directly by the strike.

The Detroit show, officially the North American International Auto Show, was once one of the premier auto expositions in the world. The top executives from all major automakers, including those not based in Michigan, attended. Celebrities and musicians were often hired to add sizzle.

But several years ago, attendance began declining at auto shows around the world, and the Detroit organizers tried to refashion theirs, moving it from January to the summer. But the Covid-19 pandemic forced it to shut down completely. The show returned last year, but was sparsely attended, and many foreign automakers didn’t bother to participate.

This year the no-shows include Honda, BMW, Volkswagen, Audi and Mercedes-Benz, but the show has added new attractions. A test track for electric vehicles has a 300-foot straightaway where visitors — riding in the passenger seat with a trained driver at the wheel — can get a sense of the exhilarating acceleration of seven models, including the electric Ford F-150 Lightning pickup and the Cadillac Lyriq, an electric S.U.V.

A start-up company, Alef Aeronautics, put on display a concept for what it hopes will someday become a flying car that can “hop” over hills, or even traffic jams.

To highlight the off-road abilities of its vehicles, Stellantis’s Jeep division created a stand out of 50 pine trees, 30 tons of boulders and 40 cubic yards of dirt. There, amid the faux wilderness, Jeep introduced a new version of its Gladiator pickup.

“Even after 100 years, this city is still a home for innovating visionaries, designers, builders and adventure-seekers,” said Jim Morrison, a Stellantis senior vice president and head of the Jeep brand in North America, during a presentation on Wednesday.

Hours later, Stellantis issued a statement saying it was still awaiting the U.A.W.’s response to the company’s latest wage offer.