SEOUL -- An unseasonal surge in air cargo on a key clothing export route from Vietnam to Europe indicates shippers are turning to more expensive air freight as shipping is disrupted by attacks on vessels in the Red Sea, freight platform Xeneta said on Friday.

Cargo volumes from Vietnam to Europe surged 62% in the week ending Jan. 14 from the previous week, and rates increased by 10%, said Niall van de Wouw, chief air freight officer for the air and ocean freight rate benchmarking platform.

"This is the first signal in Xeneta data that the Red Sea crisis is impacting air freight. This is typically a quieter time of year for air freight, so to see increases of this magnitude, with higher volumes than at any point in 2023, is significant," van de Wouw said.

The Red Sea, which leads to the Suez canal, lies on the key east-west trade route from Asia's manufacturing hubs to Europe and onto the east coast of the Americas. About 12% of world shipping traffic accesses the Suez Canal via its waters.

More manufacturers are seeking to transport their products by air in the next few weeks as attacks by Yemen's Iran-aligned Houthi group on vessels force them to find alternate routes, logistics firms have said.

Freight companies have been securing more air cargo space and some customers have begun shipping goods wholly or partially by air to avoid delays.

The volume sent by air on the Vietnam-Europe route in the week ending Sunday was 6% higher than 2023's peak week in October, and 16% more than the same week a year ago, van de Wouw said.

"In the next two weeks we should know for sure if this represents a genuine and significant shift from ocean to air freight due to the Red Sea crisis," he said.