CONTRAILS, MINTRA LEVEL, DRYTRA LEVEL, MAXTRA LEVEL, DISTRAILS  

WHAT IS CONTRAILS.
HOW ARE CONTRAILS FORMED.
WHY DO CONTRAILS FORM.
WHAT IS MINTRA LEVEL.
WHAT IS MAXTRA LEVEL.
WHAT IS DRYTRA LEVEL.
WHAT ARE DISTRAILS.
CONDENSATION.
SATURATION.
AT WHAT HEIGHT CONTRAILS ARE FORMED.