14 CFR Part 382 Nondiscrimination on the Basis of Disability in Air Travel (Air Carrier Access Act) (with amendments issued through May 2016)

(e) You are not required to retrofit cabin interiors of existing aircraft to comply with the requirements of this section. However, if you replace any of an aircraft's aisle seats with newly manufactured seats, the new seats must include movable aisle armrests as required by this section. However, an aircraft is never required to have movable aisle armrests on more than one half of the aisle seats.