Boeing's new 787 Dreamliner plane has received a major boost, with an order for 50 of the aircraft from one of the world's biggest jet leasing groups.
Boeing's 787 Dreamliner is on track to make its debut in May next year
The order by International Lease Finance Corps (ILFC) at the Paris air show is part of a deal covering 63 Boeing jets worth $8bn (£4bn).
It puts the US giant back in contention after European rival Airbus revealed a raft of high-profile orders on Monday.
The two firms are vying for the title of world's largest planemaker.
Orders from plane-leasing companies - among the biggest global buyers of aircraft - are often seen as an indication of how a model will succeed in the long term.
The ILFC order - which also included 10 next-generation 737s, a 777 and an option for two more 787s - will be delivered between 2013 and 2017.
This follows a deal with General Electric (GE) on the show's first day.
GE's commercial aviation services made an order for six 777 Boeing freighters valued at about $1.4bn, for delivery in the last three months of 2008.
And a report on Tuesday said that Delta Air Lines could be poised to order as many as 125 Boeing 787 jetliners by the end of this year.
The Wall Street Journal website quoted Delta operating chief Jim Whitehurst.
However, a Delta spokesman later said that it had been having conversations "with several aircraft makers" and that "no final decision" had been made on future fleet purchases.
Stolen a march
Boeing said it had now received 634 firm orders for its mid-size 787 Dreamliner, built using modern composite materials and designed to be fuel-efficient.
Airbus says it is over the setbacks caused by the A380 superjumbo
The plane has stolen a big march on its Airbus rival A350 XWB, which had just 13 orders ahead of the Paris air show and is still in the design phase.
It is expected to debut in 2013 - five years after the Dreamliner jet's expected time of arrival.
But confirmation of an existing deal with Qatar Airway for a $16bn (£8.1bn) order for 80 A350 Airbus planes and three A380 superjumbos for about $750m has revived the rivalry between the two companies.
Airbus said it had turned the corner after a year-long crisis linked to production problems and boardroom turmoil at its A380 superjumbo project.
Speaking at the Paris air show, chief executive of the European planemaker, Louis Gallois, said: "Airbus is back."
Other Airbus orders came from US Airways worth $10bn for 22 of its A350 planes, 60 A320s and ten of its A330-200 wide-body jets.
In March, Airbus unveiled a major cost-cutting programme intended to reduce the workforce in Europe by 10,000, as well as announcing a restructuring of the group.
"I can tell you with full confidence that Airbus is back and fully back, as you have started noting yesterday as demonstrated by our first day announcements," said Mr Gallois on the second day of the air show.