I'd disagree that most airline flights still have 2-pin audio jacks, as most aircraft have seats that have been upgraded to 1-pin stereo audio jacks. The 2-pin audio jacks were an upgrade from the two-hole jacks passengers attached sound tube headphones into.

https://apex.aero/articles/sound-tube-surprising-history-airline-headsets/

Bless your heart

Well, that's uplifting news.

Don't forget the asbestos, either.

No men will be able to find the stadium.

Recirculation just keeps the HW pipes (and contents) warm, which should be insulated with foam. You can use a timer to decide when it runs. Gas heat in a tankless is pretty much instantaneous, but there is a "cold water sandwich" issue when there not enough mixing in the pipes.

Ok, so your using the electric tankless to provide supplemental heat when the tank runs cold, then. Here in California, electricity runs 35+ cents/kWh, so the relative cost is more dramatic. My local city is now outlawing gas appliances for new construction and 50%+ remodels, and they can have my natural gas tankless water heater when they can literally pry it out of my cold dead hands. I just finished my 90% remodel + 9% addition, so I'm well positioned that way.

Tankless electric use resistance heaters which costs $$$$ to use, and need high current wire and breakers which costs $$$$ to install. Tankless gas, if you've got a sufficient gas line (can go up to 199kBTU) only need a little electricity.

Could be the thingamajig, though.