The best approach is to debunk the individual claim (such as: contrails only last a few seconds), rather than trying to debunk the entire theory.
I’ve tried to arrange each section in the order of most useful links first.
Its first use was at Eglin Air Force base, Florida, in 2003.
Defence officials believed the MOAB could be used as part of the US ‘shock and awe’ strategy during the invasion of Iraq, and recorded the test to scare Saddam Hussein’s troops into surrender.
Theorists claim: Contrails used to dissipate in a few seconds, minutes at most. There’s a huge amount of evidence (in addition to lots of people remembering persistent contrails).
It dates back to 1918, and continues up to the present day.
Memphis Belle WWII Bomber Contrails – 1944 – A 1940s film that shows planes leaving contrails, including with gaps in them.