With the seaport's contribution to the economy destined to decline as it moves into its sunset years, Hong Kong's government and logistics community will find a small level of comfort in the fact that the highest-value trade - that which moves through the airport - still appears robust. As senior management at the Airport Authority are quick to point out, air cargo may represent only 1 per cent of the volume of trade moving through Hong Kong each year, but it comprises 30 per cent of the value. More than 930,000 tonnes of air cargo moved through the myriad of automated loading bays at the airport's biggest freight terminal over the past five months, up almost 5 per cent on the record performance posted last year during the same period. Hongkong Air Cargo Terminals Ltd (Hactl) is the world's biggest handler of international airfreight and growth does not come easy from its huge volume base. So, the fact that it again - for the third year in a row - is on track to set a new world record for international airfreight is testimony to its location and its management. At this pace, the new volume benchmark, against which other terminal operators must stack up, could eclipse 2.4 million tonnes by year's end. So, at least that sector of our trade is healthy and safe from erosion, right? Maybe not. Yes, the bottom line for Hactl is healthy, in tonnage terms. But a worrisome trade imbalance is growing and is not showing any sign of recovery as we move out of the slow season. While exports and transshipment cargo from Hong Kong remain strong, imports are waning. Inbound cargo, at just under 55,600 tonnes last month, comprised 28.8 per cent of the volume moving through Hactl. Import volumes were about 50 per cent of export volumes. Last month, their comparative decline was 10.3 per cent, the largest monthly setback this year, and it dragged overall import volumes down to an aggregate 7.9 per cent decline for the year. Moreover, the decline is gathering pace: Hactl's aggregate imports were down 7 per cent in the year to February and 7.7 per cent at the end of the first quarter. Augmenting the concern is the growing number of flights bypassing Hong Kong and heading directly to the mainland. When the United States and China signed their new bilateral air services agreement last year, a door opened to a flood of new freighter and passenger capacity direct to China's dominant commercial areas, particularly Shanghai. The pundits will say that Shanghai is a different market, and that is true. But the lack of availability and dependability of flights to Shanghai in the past had driven a lot of Yangtze River Delta-bound cargo through Hong Kong. Increasingly, that is no longer the case. Ask any of the express operators - which are big general cargo players until the emerging markets develop demand for more time-definite express products - and they will say one of their fastest-growing sectors is China-direct. The pent-up demand in the US and Europe was huge for China-direct capacity, because no one had been able to offer a dependable service until recently. Another factor is that China is shifting from being exclusively a product origin market to a product destination market. In other words, China's appetite for western goods is growing and foreign firms are spreading their production lines out as a result. 'In the past, a foreign manufacturer may have had eight factories in Guangdong,' a Hong Kong-based supply-chain expert told Below Deck. 'Now they have five factories in southern China and five in the north for distribution purposes.' 'A lot of the production models in China are changing to local sourcing, even for items such as the components, which used to be sourced outside China and brought in,' he said. 'Less and less is going to move through Hong Kong.' For now, strong export volume growth and a surge in transshipment cargo are masking a growing trade imbalance at the airport. As the peak season gathers steam, increasingly nervous officials at the airport will be watching to see if that corrects itself.