Kevin Diemar’s cellphone rang one recent evening. It was 9:30 p.m.; Pamela Rodriguez was frantic. Her boss, a Miami philanthropist, wanted catering service on his 7:30 a.m. flight from Miami to Anguilla the next morning.

“No problem,” said Diemar, CEO and president of Unity Jets. “I’ll take care of it.” The next morning, the philanthropist and his two traveling companions were eating bagels and yogurt as their plane left the tarmac.

Diemar founded Unity Jets, a boutique private jet brokerage firm headquartered in west Kendall, with a plan to simplify private aviation and eliminate upfront and membership costs associated with fractional ownership and jet card programs.

“You see hundreds of ads for luxury watch companies, and I always think to myself, ‘I’m the only one who can give these people what they’re really looking for — which is time,’” Diemar said. “It really is like a time machine.”

The trip-by-trip charter and payment model has paid off. In 2011, its first year of operation, the company raked in revenues of $7 million, Diemar said. Revenue has climbed steadily since: $14 million in 2012, $20 million in 2013 and $24 million in 2014. Last year, the company flew 450 clients.

Diemar started the company — wholly owned by Diemar and Chief Operating Officer Chad Howett — after working for six years with Marquis Jet, now owned by NetJets, a fractional jet ownership company that is part of Warren Buffett’s Berkshire Hathaway portfolio.

During the busiest times of the year — Christmas, Thanksgiving, Spring Break — Diemar remembers booking his Marquis clients on brokered aircraft as the number of travelers exceeded capacity on Marquis’s own fleet. The price for the passenger wouldn’t change; customers either had fractional ownership of a plane or a prepaid jet card worth a set number of hours of flying time. But Marquis spent substantially less on flights on the brokered planes than on those in their own fleet. And customers didn’t complain about any difference in service.

The economic downturn fueled the financial caution that has made Unity appealing to private flyers.

After the recession, many high-net worth fliers were wary of tying their finances up in large assets, such as fractional airplane ownership, said Brian Foley, an aviation industry market analyst with Brian Foley Associates.

Many wanted to travel privately but with less upfront financial commitment.

“The values of business jets just tanked,” Foley said. “And when you buy your share of an airplane, at the end of your term you get to sell it, but you don’t know what it will be worth.”

Today, only 4 percent of the total number of business jets — about 720 — are fractionally owned, according to May 2015 data from JETNET, said Mike Chase, an aviation analyst with Dallas-based M.D. Chase and Associates.

The charter market was hit as well; Foley estimates charter operations — the number of takeoffs — dropped about 40 percent between 2007 and 2009. The aviation market has slowly improved since then, but is still about 10 to 15 percent below what it was in 2007.

As a result, dozens of charter consolidators mirroring Unity’s basic business model have sprung up, Foley said. The experience of Unity Jets’ staff sets them apart.

“There’s really no operator that can be everything to everyone,” Foley said. “You really need to pick your niche and stick with what works for you.”

In Unity’s case, the model hinges on Diemar’s early experience. To avoid the need for consumers to invest upfront, Unity uses only aircraft that he leases from other firms on a case-by-case basis.

When a client calls Unity to charter a flight, staff members source appropriate aircraft, check safety ratings and amenities, and estimate costs and flying time. The options for the flight end up on Diemar’s desk. It’s usually littered with dozens of call sheets — pieces of paper with scribbled details about the planes available for a single route.

Diemar will select the two or three planes with the best value and propose them to the customer. Once a flight is booked, Unity’s nine-person team — based in cities around the United States — coordinate additional services as well, such as catering and ground services.

Diemar said Unity can typically coordinate flights with five or six hours notice, about the same time frame as NetJets — though tight deadlines can affect the price.

Last year, Unity Jets organized about 4,100 hours of flying time on some 1,800 legs. The company charters all types of aircraft, from turboprops for trips to the Bahamas to heavy jets for flights to Europe.

On a small seven-passenger jet, a flight from Miami to New York starts around $10,000. On a eight-passenger midsize jet, the price bumps up to $14,000 one way. Roundtrip is cheaper than two one-way trips.

For many of its clients, Unity is only one part of a larger private air solution. Some 10 to 15 percent of its clients have a jet card membership or hold fractional ownership in a jet, Diemar said.

He encourages those clients to charter for flights from major hubs — like South Florida or New York — because those markets have an abundance of aircraft, allowing for discounts of 30 to 40 percent over membership and prepaid costs. But for flights in smaller markets, he tells clients to use their memberships — those companies are already obligated to them, and they should use them if better deals aren’t available. “If you’ve already made the commitment and you have NetJets or a jet card, use me as a hedge,” he advises.

But price isn’t the only consideration.

“We know these clients, we know what makes them happy, and we’re just trying to deliver above that,” said Garrett Grossberg, Unity’s director of operations. “And, hopefully, they’ll call us the next time.”

That was the case with a recent Grammy-winning vocalist who needed to get from the French Riviera, where she was vacationing, to an awards show in Los Angeles. But it’s wealthy families and entrepreneurs — not celebrities — who are Unity’s most frequent fliers.

“I do not have the type of clientele that’s ‘typical Miami,’ showing up in a bright yellow Ferrari and blinged-out,” Diemar said. “It’s very quiet. These people, you would not even know what they’re worth, and that’s how they like to operate.

“And that’s what the word private aviation means to us.”