http://news.bbc.co.uk/2/hi/americas/3707057.stm

Are that video filmed by those pilots another atmospheric
phenomenon or just some weather-balloons in the sky ?

Without positive identification, we can't tell. However, we are
free to speculate, as long as we admit the speculation could be wrong. 
Those UFOs are unlikely to be "atmospheric phenomenon" or "weather ballons" 
as the UFOs were glowing brightly in infrared, indicating heat. They could 
be Hot Air Balloons, however.

CM