Now that AC outlets are more common on airplanes, I've been trying to keep my phone charged while on board. I'm mostly flying Airbus 320 or 321 aircraft on United or Virgin America (Alaska). I haven't found one yet that any of the outlets that grip the pins of any of my plugs snugly enough to use. They fall out in less than a minute, even without a USB cable plugged into the charger. I've tried all of the three plug-in wall wart chargers and the plug for my computer's line lump power supply and they're all uselessly loose in the outlets. I can't blame my plugs since all of them fit outlets at home and in hotel rooms (other than the ones that get a vacuum cleaner plugged in to them every day), though I have had the same problem with hotel room outlets that are built into desk lamps.

None of my tech gear is from Apple, and I only fly in coach. Do the power outlets in First Class have more grip? Or have I just been unusually unlucky with the combination of plugs and sockets?