This is fairly a good post for those who are still new to the basic of WAI-ARIA and web design standard.
Just a few additional notes for those who are interested in learning more about web accessibility for airline booking websites. Under the new Air Carrier Access Act (ACAA), it is a requirement for airlines to make their automated kiosks and websites fully accessible.
The United States based airlines must comply with the ACAA regulations to have their websites accessible to all. Foreign airlines that have established marketing campaigns in the United States and or offer services in the United States are also subject to the ACAA. For example, if a foreign airline utilizes English to describe their services and or displays pricing using USD, they must comply with the ACAA. Read it here: https://www.deque.com/air-carrier-access-act-update/
Apart from that, for those who are currently using Sketch App. Some cool dudes at Stark developed a colorblind simulator & checker. Try it out here. http://getstark.co/ Share your feedback with them. :D
Lastly, for those who are using Chome most of time. Get this extension called WAVE. It is useful for you to check if your site is access-friendly, get it here.