Several airlines still have TDD numbers, including American, Alaska, Delta, US Airways, JetBlue, and United. I helped set up the TDD service for American Airlines in 1979 at the Cincinnati reservations office. American was the first airline to have a national toll-free number for TDD. National Airlines had a regional service in the southeast earlier than that, but AA was the first to go nationwide.
Regards.
Charles G. Gray Senior Lecturer, Telecommunications Oklahoma State University - Tulsa (918) 594-8433