As aerophilatelists we collect many kinds of airmail. Here you can find 47 different categories that have appeared as Sections in the American Air Mail Catalogue from the 1st Edition in 1935 through the 7th Edition with the latest volume published in 2017. Some are exceedingly narrow like Air Labels which are unlikely to be published in the future. Others, like Contract Air Mail, are expansive and will no doubt be updated with the next edition of that catalog is prepared.
Each Section has a page to explain how the subject is collected. In addition to a representative illustration, the page also tells what editions of the Catalogue the Section has previously been covered. If it is likely to be covered in an upcoming publication the page will say so. If a member is acting as contact on the subject it will be noted.