By Agence France-Presse
Dennis Muilenberg, chief executive of the US aerospace giant, revealed the outlook upgrade to reporters in London before the sector's Farnborough Air Show starting Monday.
"We continue to see the aerospace market grow very strongly," said Muilenberg.
"We see $8.1-trillion marketplace in the next ten years" for commercial, defence and services, he added.
"We further increased our estimates in the next 20 years.
"We expect the world to need roughly 43,000 new commercial airplanes. That's up from last year's estimates."
Boeing will publish exact details of its latest outlook on Tuesday, the second day of the Farnborough event held southwest of London.
European arch-rival Airbus had forecast last week that the world's passenger fleet would more than double to 48,000 aircraft over the next 20 years, on the back of keen demand from emerging economies and low-cost airlines.
In a revised market outlook, Airbus had put the value of nearly 37,400 new aircraft required to meet global demand at $5.8 trillion by 2037.
In 2017, Airbus had estimated the world would need 35,000 new planes by 2036, valued at $5.3 trillion.
Airbus and Boeing meanwhile continue their head-to-head dogfight at the biennial Farnborough event, locked in a battle for lucrative multi-billion-dollar jet orders.