Believe it or not, Airbus is working on it. Regular people will get smaller seats than they do now, while fat people get wider seats.

“Airbus recently said in a press release it will offer extra-wide seats on its A320 planes, "providing adequate space for those who need it, while giving airline operators a new method to generate additional revenue." Instead of having three 18-inch seats in a row, the new arrangement will have one 20-inch and two 17-inch seats.”

"Under the new system, Samoa Air passengers must type in their weight and the weight of their baggage into the online booking section of the airline's website. The rates vary depending on the distance flown: from $1 per kilogram on the airline's shortest domestic route to about $4.16 per kilogram for travel between Samoa and American Samoa. Passengers are then weighed again on scales at the airport, to check that they weren't fibbing online."