Why are there cases where air transportation is more profitable than sea transportation?

The cost of flying goods around the world is about 2.5 times higher than before the pandemic of the new coronavirus, and it ships in major trade lanes, especially in high demand, such as shipping from China and Southeast Asia to the United States. It is said that the price is 5 to 6 times higher than usual at the peak of. Marine shipping by ship is cheaper than air transportation, but American Shipper, a news site that deals with news about logistics in the United States, explains why air transportation is still relatively advantageous.

Why is air cargo suddenly affordable relative to ocean shipping? --FreightWaves
https://www.freightwaves.com/news/why-is-air-cargo-suddenly-more-affordable-compared-to-ocean-shipping

According to the Freightos Air Index , airfare from China to the west coast of the United States in the first week of November 2021 is about $ 14 per kg, and airfare from China to the east coast of the United States is about $ 13 per kg. The price is (about 1400 yen), which is about twice that of the same period of the previous year.

The global epidemic of the new coronavirus has severely constrained people's movements, significantly reducing the demand for passenger planes, and at the same time, airlines have significantly reduced the number of flights. In late 2021, the epidemic subsided and demand for planes picked up again, pushing airlines to recover, but international air cargo capacity was about 70% lower than before the pandemic. And that. The cost of air transportation has doubled because the number of planes that can be used for air transportation has decreased.

On the other hand, the demand for marine transportation to the United States is also increasing, and it is said that it has increased by more than 20% compared to 2019. However, the shipping company and the port are overburdened, resulting in large-scale delays and port stagnation. As a result, marine transportation costs are also rising significantly compared to before the pandemic.

For example, at Los Angeles Harbor and Long Beach Port, which are the main ports on the west coast of the United States, as many as 80 container ships have been stranded waiting for berthing, and in October 2021, Los Angeles Harbor and Long Beach Port were opened. We have announced a policy of imposing an additional charge of 100 dollars (about 11,000 yen) per container per day for stays of 3 days or more.

The advantage of air transportation is that it can be transported much faster than sea transportation, and the disadvantages are that the transportation volume is smaller and the transportation cost is higher than sea transportation. For this reason, it is limited to perishables, expensive items, and other items that are profitable even at extra cost, and is usually shipped by sea rather than by air.

However, due to the influence of the pandemic, the cost increase of marine transportation has exceeded that of air transportation. Before the pandemic, the transportation cost per kg by air was 13 to 15 times that of sea transportation, but at the time of writing the article, it was only 3 to 5 times. Therefore, depending on the situation, there are cases where air transportation has better cost performance than sea transportation.