Since 2019, people have been welcoming the warmer months as “hot girl summer,” a phrase that went viral before Megan even released the track with the iconic moniker. The summer anthem sparked an association with a carefree mindset, and an ability to live without a worry to what others might think. People on social media would document their summer travels with the caption “hot girl summer,” as one would have said they were “summering” in a bygone age.

Seven years, a pandemic and a long-running cost-of-living crisis later, people are wondering if “hot girl summer” is bygone itself as the jet fuel crisis, stemming from the simmering conflict in Iran, means that your super sporadic, last-minute friends are going to feel it the most. “It’s still on. Just keep it flexible,” Hayley Berg, lead economist at Hopper Technology Solutions (HTS), told Fortune. “Flexible hot girl summer.”

Berg, who has been following flight ticket prices for HTS, a company that offers weary travelers with the peace-of-mind in hassle-free bookings and refunds, said she’s seen fares skyrocket thanks to the Iran war disrupting the global jet supply, but demand is still the same as last year. In fact, domestic airfares for Memorial Day weekend were up more than 50% compared to this time last year, according to data from HTS. This year’s jump is being driven by a sustained disruption to global jet fuel supply tied to the effective closure of the Strait of Hormuz and the ongoing conflict in Iran.

“Prices always spike at the last minute for a weekend away,” Berg said. “The difference is prices are over $100 more expensive now than they were at the last minute last year.”

A sustained shock

Jet fuel typically accounts for 15% to 30% of an airline’s operational expenses in the United States. Short-term disruptions to supply, say a refinery incident or a brief geopolitical flare-up, don’t usually trickle down to the consumer in any noticeable way. Airlines absorb the cost, prices stabilize, and travelers move on. But this year, it’s different.

“That’s typically how I think about whether there’s going to be a fuel impact and how big it’s going to be. Is it a shock, or is it significant and sustained?” Berg said. “And this is significant and sustained. It started slowly, but as this conflict has gone on, it has definitely settled in and is more extreme.”

Fuel prices have increased somewhere in the range of 50% to 100%, and that cost is now hitting the ticket price. Airlines held off as long as they could: it is peak booking season after all, and no carrier wants to scare off customers who are already facing higher costs across the board.

“Airlines absorb what they can in their bottom line, and then they pass on what they can’t,” Berg said. “I think there was some hesitancy initially to pass on higher prices when customers are already facing more headwinds. But now the costs are too great. They’re going to have to be passed on.”

How fares really work

For anyone wondering whether airlines are dynamically jacking up prices every time you search, Berg says that’s not how it works, and understanding the mechanics actually helps explain why the fuel impact took a few weeks to fully show up in fares.

“Something I hear often is, ‘I searched for a flight, and then they used cookies, and they changed the price when I shopped 10 minutes later,'” she said. “That doesn’t happen. Airlines are not actually that flexible. They file fares on an internal schedule. Sometimes once a day, twice a day. At most in the U.S. you can file every maybe four hours. So if there’s a one-day shock to jet fuel prices, airlines aren’t going to change the price 10 minutes later. They have to file the fares, and then the fares are rolled out and made bookable.”

That built-in lag means airlines have some buffer against short-term volatility. But when the underlying cost increase is sustained, the higher prices eventually work their way through.

Last-minute travelers will get hit hardest

Flights departing soon are absorbing the full force of current fuel prices. Flights further out, say late August to early September, still carry some uncertainty about where fuel costs will land by then, which gives airlines a reason to price them more moderately, at least for now.

“We have seen pretty significant impact in short-term flights, so flights that are happening soon,” Berg said. “The impact is a little bit softer in further out flights, where it’s possible that by the time that flight happens, fuel will be less expensive. End of summer, early fall prices are going to be a little less impacted.”

That’s cold comfort for anyone booking a last-minute Memorial Day getaway. But it does create a real strategic advantage for travelers willing to be flexible about when they go.

Berg’s advice for summer travelers is the same playbook she’d recommend any year. She says to avoid the peak weeks: the last two weeks of June and first two weeks of July are the most expensive window of the summer. If you can push your trip to the last two weeks of August or early September, do it.

She advocates for flying midweek as well. If you’re taking a week-long vacation, go Wednesday to Wednesday instead of Saturday to Saturday. Same thing with shopping across multiple airports. If you’re in a city with two airports, check both, on both the departure and arrival end. More airline options mean more competitive pricing, especially from low-cost carriers. If you’re headed to Europe, don’t fixate on flying directly to your final destination. Fly into whichever EU city is cheapest from your departure point and then use low-cost European carriers to get to Paris, London, or Rome for a fraction of what a direct flight would cost.

And most importantly, book with flexibility. If a refundable fare is available, consider it. If not, and a Cancel for Any Reason option is offered at checkout, Berg says it’s worth the extra cost, especially in a summer where prices could continue to shift and trip budgets may need to be reworked on the fly.

“If the total cost of your vacation becomes untenable because prices are so crazy, or things get really interesting this summer, just give yourself the flexibility to change your plan,” Berg said.

People are still going

Despite fares that are more than 50% higher, Americans aren’t staying home. HTS data shows that scheduled capacity for Memorial Day weekend is essentially the same as last year, at 53 basis points more, a negligible increase.

Travel, Berg noted, remains the one category of discretionary spending where consumers have consistently said they’d spend the same or more rather than cut back, even as they’ve pulled back on nearly everything else.

“That tells me that there is no great departure from Memorial Day weekend vacation,” Berg said. “People are still going. They’re probably just going to be cutting back somewhere else so they can still budget for it.” You can still have your hot girl summer, you just have to be more flexible.