RALEIGH, N.C. — Battelle, a nonprofit government contractor with more than 22,000 employees at 60 sites, has booked its employees’ trips through Travel Management Partners since the corporate travel agency was formed more than two decades ago.

Battelle spokeswoman Katy Delaney says she has memorized the phone number for the Raleigh, North Carolina-based agency’s 24/7, 365-days-a-year customer helpline.

“It’s hard traveling for business,” she said. “Adverse weather can throw things off. Security issues come up. You’re dragging around luggage and flights get canceled and you have an important client meeting.”

When those problems arise, she added, “It’s just reassuring to know when you’re out there on the road that you can call (TMP) and they’ll take care of you.”

The advent of online travel sites such as Travelocity and Orbitz once triggered talk that travel agencies were doomed. But corporate travel agencies like TMP have survived for a number of reasons, including their ability to obtain volume discounts and the complexity of traveling to multiple cities on different airlines — plus the need to book hotels and ground transportation at each location.

Many businesses have decided their executives’ time is too valuable to be “playing around on the internet” making travel arrangements, said John Lewis, TMP’s co-founder and CEO.

Since it started in 1994, TMP, which today is one of the largest corporate travel agencies in the Southeast, has earned a reputation for forging long-term relationships with customers.

“If they lose a client, it’s because it got bought by another company,” said Don Swartz, managing director of CTBR, a travel consulting firm in Florida.

TMP has survived and prospered in an industry that has been undergoing significant upheaval, said Lewis, by taking care of its 135 employees, including more than 30 at its headquarters. The agency has added about 15 employees over the last 12 months.

If you make your employees No. 1, said Lewis, the employees will make your customers No. 1.

“What we always try to do with our people is provide competitive salaries, excellent bonuses, whatever we can come up with — free trips, things of that nature,” he added.

Lewis noted that the agency’s vice president of operations and chief financial officer have been with the business since the beginning. And, to minimize layoffs during the recession when corporate travel “just dropped off the table,” he cut his own salary nearly in half for a 14-month period.

In 2015, TMP reports it booked more than $300 million worth of airline, hotel and car rentals for its roster of 40 clients.

TMP, which charges a flat fee that it negotiates with its clients based on the level of service provided, doesn’t disclose its revenue.

But Lewis did say that the agency’s annual revenue growth has averaged 10.5 percent over the past three years. So far this year, revenue is on track to rise 15 percent.

Corporate travel agencies can take the lead on, or provide support for, negotiations on obtaining significant volume discounts from the airlines, hotel and car rental companies.

Beyond those negotiated discounts, TMP’s agents “are better at finding lower fares and rates than the typical traveler who goes to Orbitz,” said Kevin Brown, TMP’s vice president of strategic sales development.

Agencies such as TMP also can configure their software so a customer’s travel policy is incorporated into the reservation process.

“Every company that spends money on travel has to have a policy that says who can travel, when they can travel, how they pay for their travel, how they get reimbursed,” Swartz said.

The dollar value of air travel booked by all U.S. travel agencies — those like TMP that specialize in corporate travel as well as those that focus on individual and leisure travel — rose 1.85 percent in 2013 and 4.02 percent in 2014. Last year, the dollar value fell 1.5 percent to $88.3 billion because of lower average ticket prices; the number of ticket transactions actually rose 6.2 percent, according to Airlines Reporting Corp.

Elanah Abrams, office services manager for Durham advertising agency McKinney, has been a TMP client since 2011.

“They work in the same way we do where you dig in and get to know (the client) you’re going to be working with, you identify their pain points, and deliver that really personal touch,” she said.