Watch those sippy cups while on a plane

Pressure changes during air flight can cause spillproof sippy cups (the ones with valves) to leak. Fill them halfway, and unscrew the top a few times during the ascent to equalize the pressure inside and outside of the cup.

Another option: use sports bottles for airplane travel.

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  1. says

    This will even happen on car trips that go through different terrain (which we learned the hard way). Open it up and ppppfpfffttttttt! My advice: always treat a sippy cup like a bottle of seltzer, and only fill it with water!

  2. AW says

    This will also happen if you leave a sippy cup in a hot car all day. Sour milk all over your front seats doesn’t make your car smell very nice. :)

  3. Terry says

    This phenomenon can happen with Dr. Brown Bottles if you place it in hot water without unscrewing the cap.

    We loved the Dr. Brown’s bottle as our 1st child would only use them, but the day care kept saying they leaked. Pish-posh. It was the science behind the design and thermodynamics… I later found this out and would unscrew the top during heating the liquid and viola!

    I imagine the pressure change would affect the bottle very simuliarly

  4. Walter Underwood says

    Even more fun, fill them with something carbonated and watch the periodic geyser action. It builds up enough pressure to overcome the valve resistance and releases a squirt. Then it does it again! Whee!

  5. says

    I’m generally dissapointed in how well those sippy cups work. They seem to fail more often than not. We’ve been more happy with the Evenflo and Playtex ones, but they’re still not great (IMO).