Kira and the Contrail ( especially for the aviators in the family)

Contrail definition according to Wikipedia:

Contrails (short for "condensation trails") or vapour trails are visible trails of condensed water vapour made by the exhaust of aircraft engines. As the hot exhaust gases cool in the surrounding air they may precipitate a cloud of microscopic water droplets. If the air is cold enough, this trail will comprise tiny ice crystals.

So Todd was telling Kira that it was time for bed and she asks if she can do the wheelbarrow (on her hands with Todd holding her feet) to her room. Todd picks up her feet and starts walking. About halfway to her room she breaks a little wind, ok, a lot of wind. Not missing a beat, she looks over her shoulder at her Daddy, still holding her feet, and says "oh look, contrails". Yeah, honey, ummm, right. Maybe mommy needs to work more on teaching science- you know standard testing time is coming up soon...