condensation trail

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A contrail; a visible line of condensation flowing from the edge of an airplane wing or similar structure.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an artificial cloud created by an aircraft; caused either by condensation due to the reduction in air pressure above the wing surface or by water vapor in the engine exhaust