Three contrails of four

Changes in the upper atmosphere weather conditions affect the shape, length, and even the presence of contrails. 

 

Three to one to two

The contrail right in back of this airplane shows it is a tri-jet engine.  Those three plumes combine into one, and then open up to two plumes. 

 

Two plumes

This twin jet engine airplane leaves a distinct two plume contrail.

 

 

Another two plumer

As the upper atmosphere weather condition changes, this twin jet engine airplane leaves a shorter two plume contrail.

 

No trail nor plume

With the upper atmosphere having very low humidity, this twin jet engine airplane overflight leaves no contrail.

 

These four flights were seen in the span of about one half of an hour.