Delta boss Ed Bastian added that the aircraft would help it improve fuel efficiency and secure a "more sustainable future for air travel".
The news comes as airlines worldwide seek to replace ageing fleets with fuel-efficient planes that emit less carbon dioxide.
Airbus and a number of major airlines signed letters of intent to explore the possibility of capturing CO2 emissions from the air and storing them underground.
Boeing revealed also that Japanese airline ANA had agreed to purchase 20 of its smaller MAX 8 jets -- worth $2.4 billion -- plus two 777-8 freight planes.
'HANDING OVER CONTROLS'
Outgoing British Prime Minister Boris Johnson opened the prestigious five-day event as the aviation sector plots its post-Covid recovery.
The event coincides with fast-moving political turmoil in Britain after Johnson's recent announcement that he is stepping down as Conservative party leader, sparking a divisive contest to replace him also as prime minister.