ToplineAs airlines pass along jet-fuel price increases to passengers, there’s an open question about how high airfares will climb as Americans plan their summer vacations.Summer airfares are up since the start of the Iran war.gettyKey FactsLooking at ticket sales for the six largest U.S. airlines, the average transaction grew by between 2% (American Airlines) and 12% (Delta Air Lines) for the week ending March 15 compared to two weeks prior, according to new data from Consumer Edge, a provider of consumer spending data.While average domestic spring airfares have risen by about 10%, summer airfares are roughly 17% more expensive year over year, Katy Nastro, spokesperson for the airfare deal-finding website and app Going, told Forbes.United Airlines CEO Scott Kirby this week told Bloomberg TV fares could shoot up 20% if jet-fuel costs remain elevated because of the war in Iran.Jet fuel, which typically accounts for up to one quarter of airlines’ operating expenses, was $3.98 a gallon Wednesday on the Argus U.S. Jet Fuel Index—up 59% since the U.S. and Israel began airstrikes on Iran 26 days ago.Major U.S. airline stocks are down roughly 11% since the U.S. began airstrikes, according to the Dow Jones U.S. Airline Index, which includes the “big four” carriers—American, Delta, Southwest and United.Has The Iran War Dampened Travel Demand?That is unclear. Airlines have insisted that travel demand remains strong despite the war. In early March, Consumer Edge saw a brief “acceleration in year-over-year growth in the number of airline bookings,” Michael Gunther, the firm’s senior vice president of research and market intelligence, told Forbes. But that growth has since returned to late-February levels, which “potentially signals that travelers tried to get ahead of further fare increases, pulling forward demand for a short period of time,” he said. “We think some of the headlines out there probably did nudge some people who were thinking about their travel to purchase their tickets,” Jeff Windau, a senior analyst at Edward Jones, told Forbes. “The data will be key in the weeks ahead to determine whether demand ends up taking a sustained hit,” Gunther said.What We Don’t KnowHow high will fuel prices go? On Wednesday, jet fuel prices were roughly $167 a barrel, based on U.S. spot prices. Kirby previously said that in a worst-case scenario, he could see oil prices rising as high as $175 a barrel and trading at over $100 a barrel through 2027. “I think fares will continue to go up in line with oil prices,” Kirby told CNBC this week. “I mean, in any business, but certainly in airlines, you’ve got to pass through the costs of the inputs” and “that requires all airlines to raise fares.” Still, Nastro says the Going app is finding summer airfare deals. “Do not wait to book your summer trips,” she told Forbes. “We don't know how much longer this is going to impact fuel prices and how big of an impact that could then trickle into airfares for summer.”Consumer Sentiment Impacts Travel DemandWhile there is a correlation between jet-fuel prices and airfares, “demand has even more of an impact,” Nastro said. Travel demand is powered by discretionary income, which is largely influenced by how well Americans feel about their financial health. U.S. consumer sentiment declined in March amid concerns about the conflict in Iran, rising gasoline prices and personal finances, according to The University of Michigan’s monthly index. While travel demand appears resilient in the near term, “it all depends on how long the conflict lasts and how quickly prices escalate,” Windau told Forbes. “If the [Hormuz] Strait remains closed longer than expected, if fuel prices stay up, all of a sudden, you potentially have other inflationary costs hitting the consumer.”TangentFlight searches on Going dropped for Atlanta’s Hartsfield-Jackson and Houston’s George Bush Intercontinental airports after days of headlines highlighted long airport security wait times due to TSA call-outs during the ongoing partial government shutdown, Nastro told Forbes.Further ReadingIran War Has Sent Airfares Climbing—Here’s What To Expect (Forbes)