The 787 will be able to do 6000'. That is as good as it gets
AFAIK. And they will be able to run higher humidity (15% vs 4%) which is a big factor also.
"With the 787 fuselage made of composite material, it's possible to increase the humidity without corroding the airplane over time. On the 787, the manmade composite material is formed and baked into large barrels that are linked together to form the fuselage. The composite material doesn't corrode as aluminum does. As a result, the 787 cabin air system will allow 15% humidity, a more comfortable level than the current 4%.
Humidity's adjustable
The 787 crew will be able to program the cabin air system for optimal humidity based on the number of passengers aboard, Sinnett says.
The cabin air will be compressed to resemble an altitude of 6,000 feet above sea level, instead of 8,000 feet, increasing the air pressure and oxygen inside the cabin.
As a result of its lower simulated cabin altitude, the 787's air will have 8% more oxygen for absorption into the blood. In studies, only 15% of passengers breathing 787-type air reported throat irritation, vs. 30% of passengers breathing traditional cabin air.
Put simply, "The lower you go, the better people feel," Sinnett says.
"The impact is more pronounced the longer the flight."
Boeing-sponsored studies have found volatile organic gases build up inside the tight confines of a plane, making some passengers feel ill. Sources include hand wipes, cologne and vinyl luggage.
As a result, Boeing has designed the 787 with not only the HEPA filters now in widespread use, but also a second filtering system that removes as many of the bad gases as possible.