As someone who has used certain types of infrared technology pretty extensively I can tell you that infrared imaging does not exclusively need to be used at night. It might work better at night in some applications but at this time of year in Nebraska and Colorado it most likely does not matter. Flying at night is most likely used for a more clandestine purpose which has obviously failed. But yeah, most likely government. Agencies/departments really don't talk to each other as much as they should.