Chemtrails, sure!

That's water vapour (cloud) and ice particles condensing around fuel exhaust when the hot, moist air exiting from the engine.

Please do your investigation on scientific sites where you can read facts backed by evidence and not only beliefs backed by speculation.

Don't just listen some random people. (don't listen to me neither!) Not sure if they are also misinformed or deliberately want to misguide others.

Here is a clue:
Condensation trails [English]
Kondensstreifen [German]

Logical questions to the others who commented:

• If the mass killing chemtrail business goes on since the 40s, than why the population more than doubled since on earth? Shouldn't be all dead already?
• Okay, it's attack against the weak. But aren't the weak dies anyway? Why someone wants to spend billions on a pointless project?
• There was not a singe "Snowden guy" exposed this, since 77 years?

Have an open mind, but don't believe everything!:)