JetBlue has raised checked bag fees to offset the impact of higher jet fuel prices amid the Iran war.

Passengers must now pay at least $39 to check a bag, up $4 per bag from the previous $35 fee. Checking a second bag now costs at least $59, up from $50. Those rates apply to bags checked more than 24 hours before departure. 

If passengers check their bags within 24 hours of departure, they will be charged an additional $10 per bag on top of those rates, according to the airline’s website.

JetBlue increased the fees as airlines maneuver to cover their rising jet fuel costs, which have soared since the Iran war began. The closure of the Strait of Hormuz has constrained oil supplies, driving up transportation costs for a range of industries. 

Brent crude, the global benchmark, rose to $115 a barrel on Monday before falling to $107.95, according to data from Oilprice.com and FactSet. West Texas Intermediate, the U.S. benchmark, rose 2% to $101.70.

“As we experience rising operating costs, we regularly evaluate how to manage those costs while keeping base fares competitive and continuing to invest in the experience our customers value,” JetBlue said in a statement to CBS News on Monday. “Adjusting fees for optional services used by select customers, such as checked baggage, allows us to continue offering more competitive fares.”

The airline added that it only increases fees “when necessary.” 

Some airlines are passing higher fuel prices on to consumers in the form of jet fuel surcharges or higher ticket prices. 

United Airlines CEO Scott Kirby last week told CBS News senior transportation correspondent Kris Van Cleave that elevated oil prices “create a lot of stress” for airlines, noting that United’s airfares have increased between 15% to 20% over the past month.  

Jet fuel costs account for roughly one-fifth of airlines’ operating expenses.