JetBlue said Monday that it is raising checked-bag fees by as much as $9 as the war in the Middle East disrupts global oil supplies and pushes up jet fuel prices. The airline said the new fees are designed to help it keep airfares competitive by charging more for optional services used by some customers, with the first checked bag now costing $39 for most domestic economy passengers and $49 during peak travel times such as spring breaks, major holidays and the summer.

The fee changes take effect Monday, with JetBlue flagging that the first bag price rises from $35 to $39 for most travelers in domestic economy. During peak periods, JetBlue said the first checked bag will cost $49 rather than $40. The airline did not suggest it was applying a fuel surcharge across ticket prices the way some carriers have, instead pointing to pricing of optional add-ons.

In an emailed statement to The Associated Press, JetBlue said that although it recognizes “fee increases are never ideal,” it “take[s] careful consideration to ensure these changes are implemented only when necessary.” The carrier said the higher charges on optional services “used by select customers” would allow it to keep its airfares competitive.

JetBlue also raised the price for a second checked bag. For off-peak periods, it increased the second-bag charge from $50 to $59, and during periods of peak demand it increased the fee from $60 to $69. The carrier said that some customers would still be able to check the first bag for free, including those who hold one of JetBlue’s co-branded credit cards and loyalty members who reach certain tiers. JetBlue also said most customers flying transatlantic routes would continue to get the first checked bag free.

The airline said its decision reflects a broader industry cost squeeze driven by jet fuel. Jet fuel is typically about a quarter of airline operating costs, and airlines have faced soaring expenses as fuel prices jumped more than 85% since the Iran war began on Feb. 28. The conflict has curtailed ship traffic through the Strait of Hormuz, a key passageway for a fifth of the world’s oil, and airspace closures in parts of the Middle East have forced some airlines to take longer routes that burn more fuel.

Argus Media data cited by the Associated Press showed the average price for a gallon of jet fuel reached $4.64 on Tuesday, up from $2.50 the day before the conflict broke out, according to Argus Media’s U.S. Jet Fuel Index. That index tracks average jet fuel prices across major U.S. hubs, including Chicago, Houston, Los Angeles and New York.

Industry analysts expect airlines to pass some of their higher fuel costs to travelers through add-ons such as checked bags and seat upgrades, since airlines do not typically add a fuel surcharge. As one airline raises fees, analysts said, others are likely to follow.

Earlier this month, CEOs of Delta Air Lines, American Airlines and United Airlines reported that higher jet fuel prices had already added about $400 million in operating costs, according to the Associated Press report.