What makes some airplanes have vapor trail and other don't?

Question

What makes some airplanes have vapor trail and other don't?

Answer 1

it all depends on the altitude that the plane is flying at... water vapor crystalizes at a certain temperature and if the temperature at a certain altitude does not meet the required temperature to make a contrail (short for condensation trail), then one will not form... however, if the temperature is at or below the required temperture to form ice crystals, then, obviously, they will form.

Answer 2

speed and altitude

Answer 3

depends on what the pilot had for dinner

Answer 4

Altitude and Moisture in the air. The more moisture the longer and more visible the contrail. The alitude has to be high enough to be below freezing temps.