Travel planning usually involves booking a trip to one place at a time.
Now a growing number of people are booking two or even three trips over the same travel period in case Covid-related problems ruin their preferred plans.
The trend is called "trip stacking," and it involves booking a more aggressive trip — say, going abroad or taking a cruise — that is backed up by a trip that's less likely to be canceled.
By planning multiple trips to different geographic areas, travelers can also pick the trip that suits their comfort level closer to the time of departure.
Trip stacking is "a fairly new trend," said Misty Belles, managing director at the luxury travel network Virtuoso. She estimates it began between May and June, after vaccinations were being rolled out in the United States, and Europe was starting to reopen.
The trend picked up steam during the summer when new Covid-19 variants started to disrupt travel plans around the globe, said Joshua Bush, CEO of the Pennsylvania-based travel company Avenue Two Travel.
He told CNBC his clients would sometimes wait six to nine months to travel, only to have their plans dashed close to their departure dates.
By early August, more than 50% of Americans had canceled or changed travel plans due to the delta variant, according to a survey conducted by the financial website FinanceBuzz.
One of Bush's clients booked a Silverseas cruise from Athens to Rome in October and a 10-day trip to Hawaii over the same period, he told CNBC.
"The thing is ... actually that Hawaii might be a little bit more of a challenge than actually going to Greece," he said, referring to Hawaii Governor David Ige's announcement last week that travelers should stay away from the state.
Mexico and the Caribbean islands are also serving as safety net destinations for Americans, because they're easy to get to, Bush said.
Belles told CNBC about a traveler who booked a trip to Portugal before it reopened, with Florida as the backup plan. Portugal opened in time, and the traveler was able to take the European trip. She pushed the Florida trip to the end of the year.
"By and large, cancellation policies have stayed really flexible, allowing the traveler to have that choice," said Belles. "But as travel starts to return in a more fulsome way, you may see that changing a bit."
Trip stacking works for some in the industry: Travelers are more likely to get their vacations, and travel agencies can earn more money when they do. Australian agency magazine "Travel Talk" published an article on the trend this month entitled, "What is trip stacking — and how can it make you money?"
But the hotels, cruise lines and tour companies on the receiving end of the cancellations may not have as much to gain.
Bush said to protect his company's relationships with its supplies, simultaneous trips are being booked for only a "small group of our very best clients." Many travelers are postponing, rather than canceling their trips, he said, and in other instances, cancellations are filled by other travelers who book at the last minute.
"Thirty percent of our bookings are within five days of departure, which is absolutely unheard of," he said. "Even internally within our own company, we're able to backfill a lot of those [canceled] reservations."
Bush said he trained his agency's 115 advisors across the nation "about how we do this ethically." He added that he doesn't believe the negative impact will be large enough to cause hotels to change the flexible cancellation policies that have allowed the trend to flourish in the first place.
Jason Friedman, the managing director of hotel consulting firm J.M. Friedman & Co., said that while trip stacking may be annoying for hotels, it is "part of the game."
"If a hotel wants to extend a 24-hour no-penalty cancellation policy, then there is nothing wrong with a guest booking and then canceling within the policy," he said.
But guests must also play by the rules, said Friedman. Calling it "a two-way street," he said guests need to accept cancellation fees and non-refundable deposit policies too.
He distinguishes trip stacking from "ghost bookings" — which he described as "bored people in lockdown having fun" who book trips because there is no penalty for doing so.
"There are people that have no intention of finishing the booking," he said. "This is wrong."
Tim Hentschel, co-founder and CEO of travel technology company HotelPlanner, said that while trip stacking makes perfect sense, there could be pitfalls.
"Travelers also need to know that unlike making three or four dinner reservations and then deciding hours before where you want to go based on appetite or convenience, trip stacking will cause prices on airlines and hotels to go up for everyone," he said. "Unlike restaurants, hotels and airlines yield their prices up as occupancy levels increase."
He said he doesn't expect trip stacking to be popular with hotels.
"Some hotels may now start to charge a non-refundable booking fee upfront — like airlines do — and others may simply eliminate their cancellation policies altogether to deter people from double booking," said Hentschel.
To minimize the chances that hotels respond this way, Hentschel said there is one thing travelers can do.
"Travelers who 'trip stack' or arbitrage their travel options should remember the common courtesy of canceling all reservations and bookings as early as possible," he said. "This is the socially responsible thing to do."
In the meantime, Bush said he believes trip stacking is a short-term tactic that will end with the pandemic.
"If we do as Dr. Fauci said yesterday and get vaccinated, we'll be out of this by spring," he said.