Passengers claim that airlines often try to squeeze more seats into a plane in order to make bigger profits.

A source with China Eastern Airlines said the company had, in the past, imported all its aircraft from the West, where people were generally bigger. But the company now plans to reduce the number of seats on the new Airbus 321 by about 20 to make the seating larger and more comfortable. The number of first class seats would be expanded from eight to 20, according to the source.

Xia Hongshan, vice-dean of Nanjing University of Aeronautics and Astronautics, suggested more airlines rearrange seats to accommodate larger passengers.

"China's civil airlines always have empty seats, especially in the low season. So, it is reasonable for companies to think about reducing the number of seats, even though it might not be a small investment," Xia said.

Early this year, a China Southern Airlines aircraft delayed take-off for two hours because two passengers were fighting over seating space.

Seating arrangement on airplanes is becoming more of an issue in China because Chinese people are becoming more overweight, Wen Weiliang, director of China Health Care Association, said.

Without larger seats, more quarrels will certainly happen, he said.

Nearly 20 million adults in China are overweight, Wen said. In large cities, 30 per cent of the population is overweight. A new fondness for fatty, Western fast food is blamed as a primary culprit.

But airlines are also concerned about the profits loss that seating rearrangement might incur because aircrafts are usually full during the peak seasons, which add up to roughly one month per year.

Some companies including China Eastern Airlines have adopted a compromise scheme by placing passengers in alternate seats during non-peak seasons.

The airlines have to find a balance between profits and passengers' feelings, and there is not an easy solution to that, Xia said.