The global airfreight industry continued to grapple with an oversupply of capacity in April, as data released by the International Air Transport Association (IATA) found that year-over-year tonnage space more than doubled the amount of volumes.

IATA, the world's largest airline trade group, said yesterday that available freight ton-kilometers in April rose 6.6 percent from year-earlier figures, while volumes, measured by one freight ton flown one mile, increased 3.2 percent from April 2015 results. April marks the first month free of any data distortions from the West Coast seaport slowdown that caused massive backlogs of trans-Pacific sea freight shipments and led some businesses to switch to airfreight to get their goods in and out of the United States in a relatively timely manner.

Asia-Pacific airlines, which as the market-share leaders handle nearly 39 percent of global airfreight traffic, reported flat year-over-year demand but a 2.8-percent increase in capacity, according to IATA data. North American airlines, which rank third on the IATA list, with 20.5 percent, reported a 9.2-percent increase in capacity despite a 4-percent rise in volumes, which was a near five-fold sequential increase from the meager 0.8-percent year-over-year increase in March.

The scales were more balanced among European airlines, ranked second in market share at 22 percent. Volumes rose 6.8 percent year-over-year, while capacity climbed 5.6 percent, leaving Europe as the only one of six reporting regions with positive capacity utilization, known in the airline business as "load factor." European airline tonnage last month grew at its fastest pace since November 2013, IATA data showed.

The most extreme example of the supply-demand imbalance was in Africa, where carriers reported a 24-percent increase in capacity with no year-over-year change in volumes, according to IATA data. African airlines account for just a 1.4-percent share of global cargo volumes, IATA said. African carriers have recently reported surges in cargo capacity, primarily on the back of an expansion of long-haul operations.

The April data continues a multi-year trend of capacity oversupply that has suppressed freight yields and kept rates stagnant. In fact, the growth of capacity in April was the same as it was in April 2015. Though a positive for value-conscious shippers, it is unwelcome news for airlines or freight forwarders that aren't able to push through rate increases.

Global yields are expected to fall 6 percent in 2016, continuing a downward pattern that began in 2012, IATA said earlier this year.

As it has done for several years, IATA issued a downbeat outlook on the cargo sector's prospects, saying subpar trade lows will take their toll on the sector despite what appeared to be decent April data. "While the April uptick in demand growth for air cargo is encouraging, the overall economic environment is not," Tony Tyler, IATA's director general and CEO, said in a statement. "The decline in global trade does not bode well for cargo markets in the months ahead."

Even some seemingly good numbers were framed negatively by the group. For example, though Middle East airlines posted a 7.7-percent year-over-year increase, IATA noted that the gains were only half of what they were from April 2013 to April 2014. In addition, European cargo demand, though headed up in April, remains weak in historical terms, IATA said. Seasonally adjusted traffic in April was only 1.5 percent higher than it was in mid-2011, according to the group.