CAMBRIDGE - Emil Jacob was lying on the floor of an airplane when inspiration struck.
During a flight from Bucharest to Paris, Jacob had the good fortune to have three seats to himself, but he couldn't stretch out because the armrests were locked in place. So Jacob, a veteran of many long, cramped flights to his native Romania, put his sweater on the floor and settled in for a snooze.
When he woke up, he started contemplating the space above him.
"I was looking up at all the height, and I thought it was absurd that people are suffering down here," Jacob said. "Just a couple of steps away there is a lot of space and comfort."
So Jacob, a financial data analyst by trade who on the side runs Jacob-Innovations LLC, of Cambridge, got to work on ways to take advantage of the unused vertical space.
He eventually came up with the "step seat principle." It involves elevating alternate rows of seats, from one to five steps above the cabin floor, to give passengers more room to lean back in economy class and enough space in business class to lie down, either by sliding their legs under the seat in front of them or stretching out in pods stacked on top of each other - no sweater on the floor required.
People who regularly fly coach know there is room for improvement.
"Anyone that's trying to make the economy-class seating better is a savior, in my opinion," said Matt Daimler, founder of SeatGuru.com, a website dedicated to airplane seating.
Jacob, 41, does his design work in a Cambridge apartment with lace curtains on the windows and classical guitars on the wall, where he lives with his wife and 8-month-old daughter. He received a patent for the seat design in 2006, but has been able to devote more time to it lately - he was laid off in March from his job at an economics consulting company in Lexington.
The simplest version raises every other row of economy seats by 7 inches, a standard step height, allowing passengers to recline seats at up to a 45-degree angle (a few inches more than the 3 to 5 inches that's standard in economy, Daimler said) and elevate their legs on a foldable footrest that takes advantage of the space underneath the seat in front of them. It's a more "sleepable position," Jacob said.
The other economy seat is two steps up and can recline a few additional inches, with room under each seat to store luggage. Each seat can be partially encased in a fixed shell, with side panels for more privacy, "so that somebody doesn't snore in your face," Jacob said.
SeatGuru's Daimler sees a market for these kinds of improvements in premium-economy seating, which falls between economy and business class. Right now, he said, "The seat feels like economy; the price feels like business."