This is the third of three supplemental notices of proposed rulemaking (SNPRM) to follow-up on air travel accessibility issues discussed in the preamble of the 2008 Air Carrier Access Act (ACAA) final rule. (The first SNPRM is RIN 2105-AD96, the second is RIN 2105-AE32.) This rulemaking action would consider (1) whether carriers should be required to supply in-flight medical oxygen for a fee to passengers who require it to access air transportation; (2) whether there are reasons to preclude the carriage of service animals other than dogs and whether any changes should be made to provisions allowing carriers to require medical documentation and 48 hours advance notice from users of emotional support and psychiatric service animals; (3) whether carriers should be required to provide accessible lavatories on certain new single-aisle aircraft; and (4) whether carriers should be required to report to the Department annually the number of requests for disability assistance they receive. The proposed rule would also seek public comment on how to best address problems that individuals with disabilities are having in accessing needed seating accommodations.