Could it be
ИАС — инженерно-авиационная служба?
Here is alink to an article, it's long and in Russian but it seems that IAS as such appeared around 1942-43.
Âîåííàÿ ëèòåðàòóðà : Èñòîðèÿ âîéí : Ðîëü Âîåííî-âîçäóøíûõ Ñèë â Âåëèêîé Îòå÷åñòâåííîé âîéíå 1941 - 1945
Sergei
ИАС — инженерно-авиационная служба?
Here is alink to an article, it's long and in Russian but it seems that IAS as such appeared around 1942-43.
Âîåííàÿ ëèòåðàòóðà : Èñòîðèÿ âîéí : Ðîëü Âîåííî-âîçäóøíûõ Ñèë â Âåëèêîé Îòå÷åñòâåííîé âîéíå 1941 - 1945
Sergei












