An advance label for the 1942 APS convention in Cleveland, Ohio.
Per the Fields/Picklo listing, this is one of three varieties. It is distinguished by the "Keep 'em Flying" slogan and blue printing in the white stripes.
A second may be distinguished by a V in the stars field and black printing in the white strips.
The third uses the slogan "Buy Bonds & Stamps" instead of the Keep 'em Flying.