Two indicators in the aviation industry may be pointing to a economic downturn: declining demand for air cargo and a "peak" in aircraft orders last year, according to the executive chairman of CAPA Centre for Aviation.

Speaking to CNBC's "Squawk Box" on Monday, Peter Harbison explained that cargo demand is "typically seen as a forward indicator of ... not just the airline industry, but where the economy generally is heading."

"Cargo is now declining fairly steeply, which suggests that the economy ... is not going to look so good," Harbison said.

As the world's two largest economies remain deadlocked in a dispute over trade and technology, fears of a global recession have emerged.

Demand in global air freight markets fell by 4.7% as compared to the same period last year, according to the International Air Transport Association.

Trade uncertainties — triggered by Brexit, as well as tariff tensions between the U.S. and China — contributed to declining new export orders and the weakness is likely to persist in the coming months, according to IATA, the global trade association for airlines.

While there was a surge in demand for cargo about six to nine months ago — which gave "some kind of optimism" — Harbison maintained that the increase may just be a "one-off surge."