Airlines and cruise operators were among the worst-hit stocks on Monday as the travel sector faced up to escalating conflict in the Middle East.

Carnival and Norwegian Cruise Line were down 7.6% and 10.5%, respectively, while Royal Caribbean fell 3.3%. United Airlines slipped 2.9% and Delta Air Lines fell 2.2%

While missile strikes across the region are set to cause travel disruption, the rise in fuel prices is likely to be the bigger concern when it comes to the largest U.S. airlines and cruise operators.

Oil prices jumped around 6.7% Monday as the key Strait of Hormuz shipping route was effectively closed amid a barrage of missile strikes in the Middle East–marine fuel and jet fuel prices are also expected to rise sharply.

The disruption felt by passengers will be frustrating but likely minimal for the U.S. companies. For example, shortly after the Israel-Hamas War broke out in October 2023 Norwegian said just 4% of its cruise trips were due to visit the Middle East in 2024.

The major U.S. airlines also don’t operate many flights to the region, though they have still flagged some disruption. Delta has canceled flights between New York and Tel Aviv through March 9 in response to the conflict. United said flights to Abu Dhabi, Beirut, Dubai, Erbil and Tel Aviv may be impacted through March. 31, giving passengers the chance to rebook.

But it’s the sharp rise in fuel prices that, if prolonged, will have the biggest impact on profits for U.S. airlines and cruise companies.