IPad Apps for Airlines
I've created a slideshow of 30 airline apps running on an iPad. These include both native iPad apps for airlines including Air Canada, Air France, and American Airlines and iPhone apps that can run on an iPad, including apps for Southwest Airlines, Delta Airlines, and several more. Read on for a few additional notes!
I searched the iOS App Store for apps for each of the airlines you listed in your request, downloaded their apps, and took screenshots on an iPad. Since your request didn't specify a definition for "major airlines," I also searched for other large regional airline apps to round out the list; some other airlines do have iOS apps, but this was as many as I could compile in the space of one standard Wonder request.
Several airlines have native iPad apps; screenshots of these apps make up the first portion of the presentation. Some airlines, such as Delta, Spirit, and Virgin, only have iPhone apps. However, since these apps can also be downloaded and run on an iPad, I've provided screenshots of these apps running on an iPad in the second part of the presentation.