Citing “significant concerns” from people with disabilities and others, federal airline regulators are weighing big changes to rules for service animals in flight.

The U.S. Department of Transportation said this month that it wants feedback from the public on possible alterations to service animal regulations under the Air Carrier Access Act.

Specifically, transportation officials want to know if emotional support animals, psychiatric service animals and other types of service animals should be treated differently from each other and if there should be limits on the species, size or number of service animals that can fly with a person. In addition, the Transportation Department notice asks if owners should be required to confirm that their service animal is trained and questions if leashes or harnesses should be mandated.

The request for public comment comes after several major air carriers moved in recent months to issue new policies on service and emotional support animals following a significant uptick in passengers bringing such animals aboard. Delta Air Lines, United Airlines and American Airlines have all announced policies since the start of the year that they say are designed to curtail problems with biting, urination and other misbehavior.

“The department recognizes the integral role that service animals play in the lives of many individuals with disabilities and wants to ensure seamless access to air transportation for individuals with disabilities while also helping to deter the fraudulent use of animals not qualified as service animals,” the Transportation Department said in announcing its effort to seek public feedback.

Previously, a Transportation Department advisory committee tasked with addressing accessibility was unable to reach a consensus on how to tackle the issues surrounding service animals on airliners.

In addition to soliciting comment, transportation officials also issued an “interim statement of enforcement priorities” this month related to service animals outlining the agency’s current procedures.

The Advance Notice of Proposed Rulemaking on Traveling By Air with Service Animals is up for public comment for 45 days.