The U.S. military is way ahead of you, they've been used for extended surveillance in war zones since 2004: http://www.nytimes.com/2012/05/13/world/asia/in-afgh

The U.S. military is way ahead of you, they've been used for extended surveillance in war zones since 2004: http://www.nytimes.com/2012/05/13/world/asia/in-afghanistan-spy-balloons-now-part-of-landscape.html http://www.nytimes.com/2012/05/13/world/asia/in-afghanistan-... and even domestically: https://theintercept.com/2017/04/24/nsa-blimp-spied-in-the-united-states/ https://theintercept.com/2017/04/24/nsa-blimp-spied-in-the-u... And before that, I believe surveillance blimps have been used in some form or another since the 19th century.