Which act primarily addresses accessibility on commercial airlines?

The Air Carrier Access Act is the correct response because it specifically focuses on the accessibility of transportation services provided by commercial airlines. Enacted in 1986, this legislation prohibits discrimination against individuals with disabilities in air travel, ensuring that airlines provide equal access to the services and facilities necessary for passengers with disabilities. This includes provisions for accessible bathrooms, seating arrangements, boarding assistance, and accommodating service animals.

In contrast, the Americans with Disabilities Act is broader in scope, encompassing a wide range of public accommodations and services beyond just air travel. Section 508 pertains to federal agencies and their requirement to make their electronic and information technology accessible. The 21st Century Communications Act mainly addresses issues related to telecommunications and online services, without a specific focus on airlines. Thus, the Air Carrier Access Act is uniquely positioned to address the specific needs related to accessibility in the airline industry.