Unlock debit card in airplane mode?

Yes because you are informing the bank that you are unlocking the card.

Yes, you need access to the Internet via WiFi. Incidentally, there's no need to keep airplane mode on - you can just turn off data roaming - it's in your phone settings. That way you can still also receive text messages. Obviously if you answer a call you will pay roaming charges, but you can just decline or let it ring out.

While I agree the answer is that it does need to be able to communicate with Capital One (via wifi or cell data), there is a way to test it.

My phone stays on wifi via a "hot spot" while remaining in airplane mode.

Yes, airplane mode can leave wifi and BT connections "active", but you can switch to airplane mode and also disable wifi and/or BT and run your own tests.

I think you will find you get a connecting to CA error or similar, but if you want to be 100% sure, give it a test.

I will just have to remember that if I need to use an ATM while in Italy, I will unlock my debit card while on my hotel's wifi before heading out for the day then relock it after returning back to the hotel. I typically carry only my credit card for purchases but keep my debit card in the hotel room safe. I am hoping that the hotel wifi is safer than wifi access at a cafe or airport... but maybe I'm just a fool.
Rick Steves' suggests using Bankomat ATMs associated with banks to avoid higher exchange fees and have safer transactions. My plan now is to avoid using the ATM at the airport upon arrival but wait to check in at the hotel to unlock my debit card and then find a bank ATM to get Euros.
I will try Simon's suggestion to turn off airplane mode after exiting the plane and turn off data roaming to have access to texts and avoid my mobile service provider charging me $10 for each 24-hour period if I access data usage.
I'll be using WhatsApp to send/receive text messages via wifi connections where available.

There is the danger of getting a little paranoid about public WiFi. Is there a risk? Yes. Is it a significant risk? Not really. I use hotel WiFi pretty much every time I travel, and have never had an issue. If all you're doing is using your bank's mobile app, you have little to worry about - bank apps use SSL encryption to secure transaction data, and most require two factor authentication to operate (app based authentication is more secure than SMS, but that's another story).

If you are really concerned, you can use a VPN to further secure data sent over Internet (either WiFi or mobile data).

The point made in the previous post is a good one - make sure your phone is locked via biometrics or secure PIN in case it'snlost or stolen, although even if it'd not, the bank app itself will be secure.

My phone needs face recognition to open and my bank apps also need face ID to open. I've previously accessed my bank apps while in Europe. I check my bank balance occasionally while on the hotel wifi. I have many autopayments set up to pay from my checking account for recurring bills... water, gas, electric, sewer, mortgage, HOA, and credit card monthly balance. I get notified via text or email when payments have been made. I've never had any problems with logging in to view my bank account via the app when using the hotel wifi.
Now I know I need wifi/internet connection to unlock my debit card to withdraw Euros at an ATM.
Thank you all for the information. So helpful... and reassuring.

Rick Steves' suggests using Bankomat ATMs associated with banks to avoid higher exchange fees and have safer transactions. My plan now is to avoid using the ATM at the airport upon arrival but wait to check in at the hotel to unlock my debit card and then find a bank ATM to get Euros.

Do you use an ATM in the US? Do you use the "off/on/off" method in the US? I don't use that feature, but I also don't use my debit card very often. In my opinion, using an Italian bank ATM is generally as safe as using an American bank ATM, and Rick's suggestion to use the Bancomat is a good one. Another, all things "equal" is to use an "international" bank - Deutsche Bank or BNP Paribus or similar large European banks are safe bets to use and will either be affiliated with Bancomat or Visa/Mastercard or similar networks. Bank of America (and other banks but not Capital One) also have "partner" banks scattered around the world, so when in places like Europe or South America or Australia, those banks are essentially BoA banks for ATM transactions, so maybe you have a second bank account & ATM card with a bank like BoA that you could use.

For the most part, almost solely using a credit card when traveling with a limited amount of cash is my preferred method. And if the worry is about using an ATM and risking fraud/theft from the transaction, a simpler (and safer) method would to just order some Euros from Capital One in the States. You'll have the Euros you need and no extra security precautions to take.

I have €110 left over from a trip last year. I've ordered Euros in the past ahead of travel and end up with large denominations even though the bank asks if I want small denominations. I may get by with the €110 I already have to tip houskeeping and occasionally a waitress/waiter. My tour company will take care of tipping the wait staff for included meals and local guides. I rarely use an ATM in the US. I use Master Card and Visa credit cards for all purchases. Yes, I do have a 2nd debit card. It is tied to my Chase checking account. My 2 debit cards stay in my desk drawer because I never use them. So I don't hassle with locking/unlocking them in the US. I was just curious about the practice of locking/unlocking debit cards in Europe if I should need more Euros and use an ATM in Italy.

I suspect that the €110 that you currently have should be enough for your trip. Enjoy your tour.

Rick Steves' suggests using Bankomat ATMs associated with banks to avoid higher exchange fees and have safer transactions.

Not sure if that is his advice, but Bancomats are a countrywide ATM network in which most of the banks participate, not necessarily associated with a specific bank. Any of them will be fine, no need to worry if it is attached to a bank, during banking hours, or other cautions.

ATMs, for an ATM cash withdrawal also do not have varying exchange rates, they are all the same, your card determines the rate through the network the card is associated with, but typically in the range of 1%.

Do be aware of Direct Currency Conversion (DCC), that will take you from an ATM transaction dispensing cash, to a currency exchange transaction, almost always at poor rates, that must now be disclosed. Always opt to do the transaction in euros, and reject any conversion. Anything that tells you what it will be in Dollars is DCC.

Also reject any offer to check your balance, they can charge an extra fee for that, but for the most part expect you will pay a fe of a couple euro in order to use the ATM. No fee ATMs are becoming more and more rare, especially when they see your US based card.

Paul - I had forgotten about the DCC option to US$. I appreciate the reminder to avoid/decline DCC. I did not know about the fee for the option to check my balance. I never have done that since I can check my balance via my bank's app. But always good to learn these helpful, money-saving tips.