Jeep sales are on fire.

The Fiat-Chrysler brand sold almost 100,000 vehicles in May, a nearly 30 percent increase over the same month last year.

That makes May Jeep’s second best month for sales ever, behind March, when the brand sold 98,382. Sales dipped in April, but the brand still sold 82,641 vehicles, eclipsing its record April 2016 sales figures.

In 2014, just four years ago, Jeep sold about 1 million vehicles. By the end of this year, it expects to sell as many as 1.9 million.

Despite these sky-high numbers, Fiat-Chrysler CEO Sergio Marchionne thinks Jeep still has more room to run. Marchionne wants to double Jeep’s sales worldwide over the next 3-5 years, he said Friday.

Both the the Wrangler, Jeep’s renowned off-road vehicle, and the Compass, a smaller crossover SUV, had their best May ever, and helped push Jeep’s numbers up. Wrangler sales rose 26 percent to 25,102 vehicles. Sales of the Compass rose sales rose to 17,327 vehicles.

The numbers indicate Jeep is performing exceptionally well, while some of FCA’s other brands are seeing only slight increases in sales or declines.

Ram Truck sales were up 2 percent in May, and Dodge’s sales up 4 percent. Fiat sales dropped 46 percent, and Chrysler sales fell 18 percent.

By 2022, automotive forecaster LMC Automotive expects 97 percent of Fiat-Chrysler’s U.S. sales to be some kind of truck, SUV, or crossover, which is an SUV-like vehicle that borrows some attributes of passenger sedans and compact cars.

Jeep is benefiting in part from a larger trend across the industry, as consumers show an ever-growing appetite for trucks and SUVs.

But still, Jeep is special, said Kelley Blue Book analyst Rebecca Lindland.

“It’s a brand that appeals to everyone across all demographics, all genders, all races,” Lindland said.

It also benefits from a fair amount of variety, for a brand that only makes SUVs. The Wrangler is more rugged, while other models, such as the Cherokee, are geared more toward lighter off-roading and urban use.

“As the brand portfolio continues to expand, it will only gain in appeal as it targets more and more consumer cohorts,” Lindland said.

Stronger supplies of Jeep vehicles are also playing a role in higher sales, said IHS Markit analyst Stephanie Brinley.

Jeep released the next-generation version of the Wrangler, called the JL, earlier this year. But it is still making the previous version, the JK. FCA also moved production of its Cherokee SUV, to its assembly plant in Belvidere, Illinois, which freed up space for the Wrangler in Jeep’s Toledo, Ohio, plant.

“Cherokee also has stronger supply now, as a result of that move and compared to somewhat constrained production at this time last year, and the refresh is also seeing a higher level of advertising to support the launch,” she said.

— CNBC’s Phil Lebeau contributed to this story