In the April issue of InsideFlyer, a reader wrote about his experience being seated next to an overweight passenger who was occupying half of his seat on an American Airlines flight. When he asked the flight attendant about the airline’s policy for overweight passengers, he was told that American does not have a policy.

As promised, we researched the policies of several carriers in the U.S. and below is what we found. We should point out that in all instances, regardless if a person must purchase more than one seat for themselves, they earn miles on only one seat.

American deals with each situation differently and does not, as our reader found out, have an official policy, “We recognize that passengers come in all shapes and sizes and we do our very best to provide a comfortable ride for everyone aboard. When faced with a seating issue which requires our attention, our airport and inflight personnel have guidelines they follow to assist them in reasonably resolving the matter to everyone’s satisfaction. Each situation is handled individually with utmost professionalism and discretion.”

Southwest has a very clear policy that is stated on its Web site. If a passenger is unable to lower the armrest between the two seats, the passenger is required to purchase an additional seat. If the flight does not oversell, Southwest, unlike most other airlines, will refund the cost of the additional seat after travel.

Continental also has a policy stated on their Web site. Customers who significantly encroach upon adjacent seating space, require more than one seatbelt extension or are unable to remain seated with the armrests lowered are required to purchase an additional seat or upgrade to first class.

Northwest and Delta both require passengers who require more than one seat to purchase an additional seat. Delta stipulates “When a passenger requires more than one seat, our policy is to charge for all seats occupied. When making reservations, many customers recognize their own need for more space and ask to purchase two seats. They are charged double the applicable fare they would pay for one seat.”

Frontier expects to have a policy in effect within the next several months but currently does not have one, “Due to an increase in the number of passengers requesting information about the purchase of two seats to ensure a more comfortable flying experience, our management team is currently evaluating a variety of approaches to dealing with this issue.”

At US Airways, extra seats can be purchased at the passenger’s discretion, but passengers of size will be accommodated at no charge if a second seat is required and available. If the flight is full, the passenger will be offered the next available flight that has space to accommodate an extra seat. If the flight is full but seats are still available for sale, the passenger can choose to purchase an additional seat.