Airbus had a few setbacks over the weekend, but it whipped up much excitement with talk of a supersonic "commercial rocket plane" ahead of the Paris Air Show, which opened on Monday. The aircraft is meant to be a greener replacement for the retired Concorde.

Airbus has a new dream, and its name is ZEHST (Zero Emission High Supersonic Transport). Design plans detail a "hypersonic" commercial jet that can carry up to 100 passengers while cruising at 4,200 kilometers per hour (2,600 miles per hour) at an altitude of 32 kilometers (20 miles). The ambitious project is meant to fill the void in air travel left when the legendary Concorde was retired from service in late 2003. But its developers have another goal in mind as well -- combining three different types of propulsion systems to make it considerably more eco-friendly than its predecessor.

Since 2006, engineers at EADS, the aerospace group that owns the airplane manufacturer Airbus, have been working on the design for French and Japanese clients. During a presentation delivered Sunday, one day ahead of the Paris Air Show opening at the Le Bourget airport, EADS CEO Louis Gallois stressed that all technical problems related to the project are solvable, but that it could still take 30 to 40 years before this vision became a reality. "We're not talking about a product that we launch in the next few years," Gallois said, according to news agency Reuters. "We have to see security, integration of different technologies, how man reacts to it."

Still, that says nothing about the costs involved. As Jean Botti, the head of technology and innovation at EADS, noted, everything depends on costs and whether buyers can be found.