Flight attendants will search for passengers who can't buckle the seat belts or put their armrests down. In the United Airlines' website the company says who are found overweight 'must either purchase a ticket for an additional seat, or purchase an upgrade to a cabin with seats that address the above-listed scenarios'.
In case no other seats are available on that flight, the overweight flier will be grounded until two adjacent seats can be found on the next plane out.
The New York Daily News quoted Jack Gillotto, a 300-pounder from Danbury, Conn., as he waited for a flight at LaGuardia Airport, as saying, "It's discrimination. I understand if a person takes space from another, they should pay extra. But not an entire second seat."
However, United Airlines said that the rule is in response to the 700-plus complaints it received last year about obese travellers invading neighbours' space.
United spokeswoman Robin Urbanski Janikowski said: "This will apply after all other solutions are exhausted. Should the flight be full, which is rare in today's economy... we will offer the second seat on another flight at the same fare that was originally paid."