Boeing trimmed its 20-year outlook for industrywide aircraft deliveries, conceding the bitter downturn in air-travel demand, volatile fuel prices and other challenges confronting airlines this year would also curb manufacturers' growth.

In its 45th annual market analysis, Boeing predicted that manufacturers will deliver 29,000 aeroplanes in the next two decades. The tally marks a 1.4 per cent decline from last year's 29,400 forecast, although inflation would help keep the dollar value of those deliveries at $3,200bn, the company said on Thursday.

“While the commercial-aviation industry is facing a significant downturn, it is cyclic and has a long history of declines and upturns,” Randy Tinseth, vice-president of marketing for Boeing Commercial Airplanes, stated. “Over the past 30 years, through both tough and good times, traffic growth has averaged more than 5 per cent per year.”