The airline websites that I've used are remarkably bad with their UI/UX. Far from any grandma being able to use it, definitely. I can rarely get through the process without some inexplicable error or missing field that I can't find or misbehaving custom date picker.

Are you asking? No they are not the same. Sure they take in the same input, but boy they can figure it how to do it differently

They are not the same because the obnoxious ads and promotions are in a different place. Navigating around them requires mental gymnastics.