Checking a bag on United Airlines now costs $10 more as Iran war sends jet fuel costs up nearly 100% in major hubs

Most travelers flying with United Airlines will now pay $10 more to check their luggage beginning on Friday, as rising jet fuel costs driven by the war in the Middle East pushes another major U.S. carrier to increase fees.

Customers traveling in the United States, Mexico, Canada and Latin America will now pay $45 for their first piece of luggage and $55 for their second bag, according to United.

“This is the first time in two years the airline has raised bag fees,” United said in a statement.

Some passengers will still receive a free first checked bag, including co-branded credit card holders, certain loyalty-tier members, active military personnel and travelers in premium cabins. Customers who check bags less than 24 hours before departure will pay an additional $5.

United joins JetBlue, which raised checked baggage fees on Monday by up to $9 during peak travel periods, as the war in the Middle East continues to severely disrupt global oil supplies, particularly near the narrow Strait of Hormuz where a fifth of the world’s oil typically passes. That has caused crude prices to fluctuate wildly, which affects airlines’ operating costs because the fuel their aircraft rely on is refined from crude oil.

JetBlue said charging more for optional services used by select customers helps keep base fares competitive. Like United, it will continue offering a free first checked bag to some customers.

The average price for a gallon of jet fuel in Chicago, Houston, Los Angeles and New York reached $4.88 on Thursday, up from $2.50 before the conflict began on Feb. 28, according to Argus Media. The energy market intelligence company’s U.S. Jet Fuel Index tracks the average prices across those major hubs.

Speaking to investors last month at a conference, United CEO Scott Kirby said the higher jet fuel costs had already added roughly $400 million to operating costs. The CEOs for Delta Air Lines and American Airlines reported similar figures.

Fuel is typically the second biggest expense for airlines after labor. Analysts expect U.S. airlines to pass higher fuel costs on to travelers by increasing add-on fees or ticket prices since they don’t usually have fuel surcharges, while a number of non-U.S. carriers already have added fuel surcharges.

This story was originally featured on Fortune.com