Mr Alan Mulally, Boeing Co's senior vice president in charge of commercial aircraft operations, said the recovery in the civil aviation industry may take longer than expected but that, for now, Boeing continues to expect the market to trough in 2003.
"Most people think that the recovery (in the airline industry) is going to be even slower because of the economy coming back slower, travel coming back slower and because of this overhang of terrorism," Mr Mulally told reporters at a meeting ahead of the Farnborough Air Show.
"All of our (aircraft) production is based on the economy coming back, travel coming back and the airlines getting help. We still think that the low point in production to support the airlines will be 2003 but that can easily move to 2004 the way it is going," he said.
But he also emphasised that this possible delay in recovery has not led Boeing to alter its plans to produce 380 aircraft this year and 275-300 in 2003.
As for 2004, Boeing will not decide on the numbers of aircraft to be built until the end of this year.
Mr Mulally's remarks mirror comments by sector analysts, who said that, while airline passenger statistics are improving, they are doing so more slowly than expected.
JP Morgan analysts recently warned that as airline reports on passenger numbers continue to show only lacklustre improvement, "we hold to our belief that the current downturn will persist for an extended period of time."
And Morgan Stanley analyst Heidi Wood expects the commercial aerospace cycle to trough in 2003 or early 2004.
In contrast, Philippe Camus, chief executive of the European Aeronautic Defence and Space Co NV, the parent company of Boeing rival Airbus, said deliveries of Airbus aircraft are set to rise again in 2004 after stagnating at around 300 for two years.
"After the first half of 2002 we are more comfortable," with the forecast deliveries of 300 aircraft for 2002 and 2003. "And we now see an increase in the aircraft that we will deliver in 2004," he told reporters at a briefing on Friday.
EADS owns 80% of Airbus and BAE Systems PLC holds the remaining 20 per cent.