NEW YORK (NYTIMES) - This should be the heyday of independent hotels, which by their very nature offer the distinctive experiences sought by many travelers.

Instead, they are up against huge hotel companies with deep pockets as well as competitors on Airbnb. The result? More independent hotels are either joining the big chains or shutting their doors.

Thirty years ago, about two-thirds of all hotels were independent, according to the hotel data company STR. Today, less than 40 per cent are independently owned and run.

One of the biggest reasons independent hotels are disappearing is that they're being acquired by the large hotel companies or joining them as affiliates to tap into their marketing power.

Accor had 3,600 hotels and 14 brands in 2013. Now, through acquisitions and investments in other lodging companies, it now has nearly 5,000 hotels under 39 brands. The chain IHG was also one of the first to the trend, buying the boutique hotel company Kimpton in 2015.

Marriott International's purchase of Starwood Hotels & Resorts in 2016 included the acquisition of the Luxury Collection and Tribute Portfolio. These groupings of affiliated hotels, known as "soft brands," get access to the big companies' reservation and marketing resources but keep their individual identities.

Marriott has had its own soft brand since 2010, the Autograph Collection, which now includes more than 175 independent upscale and luxury hotels worldwide, among them the Emery Hotel in Minneapolis and the Publica Isrotel in Tel Aviv. Nearly 90 more hotels are in the process of joining the Autograph group.

From a customer standpoint, the clear demarcation between a chain and an independent hotel has totally eroded, said Jan Freitag the senior vice president for lodging insights at STR. When a guest walks into a hotel, he said, it's not apparent that "it may be powered in the back by an affiliation."

The big chains have been expanding their soft brands to meet the needs of travelers looking for "unique, boutique or historic" places to stay or to add a smaller or different-priced offering to a market where the company sees an opportunity, said Ting Phonsanam, a founder of Momentum Hospitality Management. His company works with independent hotels to strengthen their brands, help develop renovation plans or prepare their properties to join a soft brand.

Independent hotels that join a soft brand keep much of their own personality, Mr Phonsanam said. "They can make their own decisions on uniforms, dining offerings, furniture and other aspects of the hotel," he said.

The fee can be significant, commonly 5 per cent to 10 per cent on all revenue, Mr Phonsanam said. In return, soft brand members receive help with marketing and can take advantage of the larger company's purchasing power or property management software.

Joining a soft brand can grow even more expensive, though, if the hotel requires significant renovations or operational changes as a precursor to joining the group.

There's also significant competition from Airbnb, said Jeffrey Low, founder of Stash Rewards, which offers a loyalty rewards programme for independent hotels. Airbnb is adding inventory to the alternative lodging market, attracting customers "who might otherwise choose an independent hotel," he said. That drives down the prices independent hotels can charge, Mr Low said.

Independent hotels with strong established positions in their markets are the most likely to reject offers to join a larger group.

Barbara Malone, an owner of the 110-year-old Hotel Sorrento in Seattle, says the key to success for the independent hotel she owns with her husband has been to "stay true to the hotel's DNA as a community builder," offering music and literary events and serving their core customers including families coming to the area for medical treatment. At the same time, she said, it's important to stay nimble and take advantage of new opportunities, like the current expansion of Seattle's convention center just a few blocks away.

Still, she said, it's becoming more challenging to operate as an independent hotel. "The major brands can approach corporate clients with a large portfolio and a range of prices," she said. "That's stiff competition." The Sorrento also competes with a growing number of Airbnb offerings and other short-term rentals.