Airlines are grappling with shortages of jet fuel at some smaller airports in the western U.S., where a travel boom is coinciding with high demand for that fuel to fight wildfires.

Many carriers during the pandemic added flights to destinations that became popular among travelers looking to avoid congested cities. But getting enough fuel to some of those airports has grown harder in recent weeks due to a dearth of truck drivers and insufficient space on pipelines, airline officials have said. At the same time, there is growing competition for jet fuel in the region from planes that fly over wildfires and drop water and retardant to squelch blazes.

Major hub airports that have connections to pipeline infrastructure and space to store fuel are less likely to face disruptions. But supplies have been touch and go at a handful of smaller airports, including in Bozeman, Mont., and Fresno, Calif., airline and airport officials said. About 18% of flights at Bozeman Yellowstone International Airport were delayed or canceled on a recent Sunday due to slow fuel deliveries to airlines, said airport director Brian Sprenger.

The jet fuel shortage is the latest challenge to the industry and consumers alike as a travel boom this year has collided with labor shortages and other logistical challenges as airlines try to revive a business hobbled by the pandemic. There is some indication the jet fuel problems could spread beyond the West.

A year after one of the worst wildfire seasons in California’s history, the state is taking more preventive measures to reduce wildfire risks. But experts worry it still doesn’t have the firefighting and land management resources to adequately fight worsening blazes. Photo: Noah Berger/Associated Press The Wall Street Journal Interactive Edition

American Airlines Group Inc. told pilots in a memo Monday that jet-fuel delivery delays initially affected mostly western U.S. cities but had started to spread. The airline said it might have to add fuel stops to certain routes and told pilots they may need to carry extra fuel on some flights. The airline instructed pilots to conserve fuel when possible, according to a memo to pilots that was previously reported by CNBC.

“Every gallon of jet fuel saved is helpful,” the airline wrote.

Jessica Gardetto, a spokeswoman for the National Interagency Fire Center, said firefighting activity hasn’t been hindered. While some locations have seen shortfalls, she said, they have been worked out quickly. It isn’t unusual for small, often hard-to-reach sites where firefighting aircraft obtain fuel to run low or run out when demand is high, she added.

Phillips 66, a refiner with plants in the Northwest, said it is giving priority to delivery of jet fuel for aircraft involved in firefighting while continuing to address customer needs.

Refiner Phillips 66 said it is giving priority to deliveries of jet fuel for aircraft involved in firefighting.

Refiner Phillips 66 said it is giving priority to deliveries of jet fuel for aircraft involved in firefighting.

Photo: H. Rick Bamman/Zuma Press

Wyoming’s governor signed an emergency order allowing truck drivers to stay on the road longer to deliver needed fuel, citing rising travel and the potential for fuel shortfalls during wildfire season. State transportation officials said the move was meant to help prevent potential problems. The state hasn’t experienced major fires or fuel shortages this year.

Nevada’s Reno-Tahoe International Airport currently presents the most acute issue for airlines. There are more flights there now than in 2019, but airlines say they aren’t able to get as much fuel from a pipeline that serves the airport. Fuel inventories at the airport are “precariously low,” a coalition of passenger and cargo carriers, airline trade groups and others wrote to the Federal Energy Regulatory Commission on Monday. They asked the commission to help boost jet fuel shipments on the pipeline.

“Unless more jet fuel can be delivered to [the Reno airport] in August, airlines could be forced to cancel flights,” wrote the group, which also included the Reno-Tahoe Airport Authority and a major fuel provider. Southwest Airlines Co. and Allegiant Travel Co. said flights to the airport are carrying extra fuel to avoid having to fill up there.

The supply constraints aren’t the first hiccup as airlines have rebuilt operations during the coronavirus pandemic. Airlines have scrambled to bring back workers to help handle the crush of demand in recent months. Volatile weather and staffing shortages have caused cancellations and delays. Travelers have faced long waits for customer service, security screening and airport coffee as airlines and airports have struggled to fill positions.

In Reno, the fuel problem is partly the result of airlines curbing use of jet fuel last year as they scaled back flying due to dwindling demand. Because of the way space on the pipeline is awarded—based on shipments in the previous 12 months—airlines say they are now struggling to get enough capacity. The airport isn’t a major hub, but in the letter to FERC the group warned that similar problems could arise at other airports as demand rebounds.

A scarcity of drivers has slowed deliveries of fuel to Reno-Tahoe International Airport from refineries in the San Francisco Bay Area.

A scarcity of drivers has slowed deliveries of fuel to Reno-Tahoe International Airport from refineries in the San Francisco Bay Area.

Photo: David Paul Morris/Bloomberg News

Kinder Morgan Inc., the pipeline’s operator, said it can’t dictate what products move through its line; that is up to shippers. A significant increase in jet fuel deliveries to Reno has been scheduled for August, the company said.

Airlines have a number of ways to deal with fuel supply problems without major disruptions to their operations. After a cyberattack hobbled a major fuel conduit in the eastern U.S. in May, carriers added stops on some long-haul flights and carried extra fuel to avoid coming up short.

In Reno, there are fewer good options, airline and airport officials have said. Heavier planes laden with fuel need longer runways, but Reno’s longest runway is closed for construction. With nearby airports also short on supplies, fuel stops are more complicated. Carriers have been trucking in fuel from refineries in the San Francisco Bay Area, but a shortage of drivers available to make the 440-mile round trip has slowed deliveries.

Tom Kloza, global head of energy analysis at the Oil Price Information Service, said many airports—particularly those that aren’t hooked up to pipelines and receive jet fuel by truck—don’t have more than a few days’ worth of fuel on hand. While the constraints are most evident in the West, the problem has arisen at airports elsewhere in the country, including Burlington, Vt., this month.

“It’s very much hand to mouth,” he said.

Write to Alison Sider at alison.sider@wsj.com