aethra (noun F) : αἴθρα [v. aestas]
* The upper, pure air, the bright, clear, serene sky: aetheris splendor, qui sereno caelo conspicitur,Serv. ad Verg. A. 3, 585 (poet.): flammea, Jul. ap. Macr. 6, 4 (Trag. Rel. p. 228 Rib.): siderea,Verg. A. 3, 585.
* Transf., like aether, the sky, air, heavens: surgere in aethram,Lucr. 6, 467: volans rubrā ales in aethrā,Verg. A. 12, 247; so Sil. 4, 103; Stat. S. 1, 2, 135 al. (but in Cic. N. D. 2, 15, 42, the correct read. is aethere, B. and K.).

s. TLL