The airlines are subject to new rules for service dogs who are doing airline travel, to take effect on December 30th, 2020. The full details are on a PDF at the US Department of Transportation's website, but the main things to know are:

• No more "Emotional Support Animals" (just full-fledged service dogs)
• Service dog handlers need to fill out this form when they fly, called the "U.S. Department of Transportation Service Animal Air Transportation Form." Here it is in JPG version, and in PDF form.