SAN FRANCISCO (KGO) -- A San Francisco man says he was asked to move out of an airplane exit row on an Asiana Airlines flight because of his prosthetic leg.Tim Seward took cell phone video of the Asiana Airlines employee who he says asked him to move from his assigned exit row seat to another seat because of his prosthetic leg.He says it happened Sunday on a flight from Beijing to Seoul.Seward says he paid extra for the seat, with extra leg room, has sat in exit rows many times and is fully capable of performing exit row duties."I cannot prove your leg is functional," a flight attendant says to Seward. "You cannot prove my leg is functional?" Seward asked, to which the attendant responded, "No, I cannot prove it.""They threatened me that they were going to kick me off the plane if I didn't move," Seward said. "Personally I feel like it wasn't right to have someone determine for me my physical ability and I think that airline should understand that that is wrong and they discriminated against someone."A cabin safety document on the FAA's website has guidelines on passengers with prosthesis sitting in exit rows."If a passenger with prosthesis is being evaluated for assignment to an exit seat, the presence of the prosthesis would not be the determinant for being able to meet the criteria but rather the physical ability to perform the exit seat duties."We reached out to Asiana Airlines for comment and have not yet heard back.