Getting into an airline seat can be as tight as skinny jeans for some people, and if you want to buy extra hip room the way airlines sell extra legroom in coach, you're out of luck. Airlines won't give an inch.

Airbus thinks it has a better idea, outlined in this week's Middle Seat. The European airplane maker has designed coach seating for its A320 family of jets with an extra-wide aisle seat and slightly narrower middle and window seats. A320 coach seats are uniformly 18 inches wide, and Airbus wants to take one inch off...