What do I lose by keeping my iPhone in 'airplane mode' the entire trip?

Is there an Apple store in your area? Drop in and have a chat. Try searching the Apple user forums for advice (which ain’t easy).

EDIT: If you are in airplane mode, part of your GPS is not active so your photos will have spotty location data. You might be better off deactivating both WiFi and Bluetooth until you are in a safe WiFi location or you need to pair to a bluetooth accessory like headphones. The weird thing about airplane mode now is that you can activate any of the radios except the cellular system.

https://www.cnet.com/how-to/how-and-when-to-use-airplane-mode-on-iphone/

https://support.apple.com/en-us/HT204234

https://www.howtogeek.com/194421/what-does-airplane-mode-do-and-is-it-really-necessary/

https://discussions.apple.com/thread/5131678

https://en.m.wikipedia.org/wiki/Airplane_mode

You might want to reconsider a SIM card. With the current EU regulations there are no roaming charges within the EU. That means buying a SIM card in one EU country gives you the same access in all EU countries.

We switched our carrier to TMobile which is the best, least expensive carrier for International travel. No need for airplane mode, a new SIM card, or any stress. You use your phone the same way there that you do here at no extra cost.

If you are in airplane mode, your GPS is not active

While Iphone's don't geotag photos in airplane mode for reasons unknown. The phone does have GPS functionality for most other functions like mapping. Phone's use four methods to determine location:
-Satellite
-Cell Tower
-Wifi
-Bluetooth

In airplane mode satellite and Wifi GPS are still active so your location will still be very accurate.

It looks like TMobile could be an ultimate solution. It would be great to not have to do this worry/relearning each trip.

Thanks for the links. Sadly, no Apple Store near where we are now (WA) -- in HI we're a block away. Some interesting reading. I didn't realize that 'push notifications' would still come through (incur data charges) when in airplane mode - Yikes, if that's the case. I'll need to check my notification settings for each of the apps.

One article indicated no texting with airplane mode on, but I found this in another article: "Airplane Mode and Wi-Fi enabled - iMessage works. Airplane Mode enabled and Wi-Fi disabled - iMessage doesn't work. I double-checked this on my own iPhone." -and- "you can both send and receive iMessage and FaceTime while on airplane mode provided you have a wifi connection."

Also, I hadn't considered losing the geo-tagging of photos. I need to ponder the risk/reward of that.

I had read that it's now possible to just get one SIM card for several countries. So, yes, maybe it's worth looking into. That means I'd have a new phone number (yes?) but since I'm likely to be contacting my host first, that may not be that big a deal.

I asked the AT&T rep about what happens if I am on airplane mode, a call comes in (from a US caller), and the call goes to the phone's voice mail. Does that end up in a charge? I seem to recall that, in past years, we forwarded our phones back to our US landline specifically to avoid this. But I don't recall the details.

In airplane mode satellite and Wifi GPS are still active so your
location will still be very accurate.

Ah, I'd forgotten! -- Last trip I used the Runkeeper app while we were walking about and it recorded a 'map' of where we'd walked. Then, once we were back at our lodging, I turned on WiFi and saved the route. It's really nice to have that as a record of each day's meanderings. I'd forgotten that that worked, through some 'magic', even with airplane mode switched on.

Keri,
When I had AT&T, I refused to pay their fees for overseas service, and always just left my phone in airplane mode. I would just use WiFi and like others noted GPS still works, but regular texting would not. WhatsApp would work on WiFi. You already know about downloading maps and the like so, If you can live with treating your phone like a tablet this works just fine. If you have to keep in constant contact, say to work or something, this isn't ideal. I however, used to kind of like the idea of being unattainable. But as time moved, reservations, e train tickets, e boarding passes etc. are more and more the norm. So now i take my phone with Google-Fi.

About SIM cards your phone must be unlocked and if you got it from AT&T it's probably not. This is a much cheaper alternative than AT&T if your phone is unlocked. It's probable even cheaper to buy a local burner phone and SIM in Europe and use it there instead of the prices AT&T charges (if your phone can't be unlocked). With this method you will have a different phone number.

If you are considering switching service providers, I would recommend Google-Fi if your willing to switch to android. With an Iphone you wouldn't get all the features on Google-Fi. Like switching between carriers. But with one of their handsets you can use your phone all over just like at home. Currently prices are $20 for phone and texting, and $10 per gig of data at home or in France.

I don't have it but other's recommend T-Moble for European travel and you wouldn't need to switch to android.

Either way I'm with you AT&T charges too much to use overseas.
I hope you have a great trip!

We switched to T-Mobile about a year ago, because we got mad with Verizon. Using it in Europe was seamless.

Keri,

We’re traveling in Portugal now and have kept our phones on airplane mode since we arrived a few days ago.

I usually buy a local SIM card when I travel, but the Vodafone shop was too crowded when we arrived to Lisbon, and we were too exhausted to wait.

I’ve checked Vodafone and MEO mobile plans here in Portugal, but surprisingly neither of these offers international calls.

I may not even bother getting a SIM card.

Here’s what I did prior to my trip just in case I couldn’t get a SIM card right away.

• I downloaded Google Hangouts (Thanks to Andrew H. from Portland, Oregon!) and I’m able to make calls to the US for free, even to landlines!
  [mainly to stay in touch with my mom 😊]

• I downloaded all the Google maps we’d be needing so I could use offline.

• I also downloaded the languages I wanted on Google translate so I could use offline.

• I have WhatsApp to communicate (text or call) with family members who have android phones.

• I'm using iMessage and FaceTime to communicate with family members who have iPhones.

Have a wonderful trip!

Edited to add...
All our hotels have provided good WiFi connections.

BTW, I’ve been happy with Vodafone SIM cards on my previous two trips to Italy (2017 & 2018)

I took the RS free travel class, “Traveling with a Mobile Phone” last year at the Edmonds site. I found it to be very helpful. We have T-Mobile which made everything easy, but there's also a lot of great info for people with different phone plans that he discussed. He also shared about various technology in this class. It's where I first heard about TripIt, and it's been a great organization app for me.

Here's the link, so you can listen/see the same class:
https://www.ricksteves.com/watch-read-listen/video/travel-talks/mobile-device

I have to preface by saying that I do not have an iPhone, an Android instead, but I did recently have a Phone under contract with ATT. When I Traveled, on landing, my phone would shut off data automatically. I still had incoming calls and texts (no charge), but outgoing calls and texts at roaming charges ($1.25 a minute as I recall, not sure on texts). I could opt to turn on data at ten dollars a day if used; you would just need to ask ATT about the options. I could not get a SIM card, since ATT phones are locked (They may have options to unlock a phone depending on contract, or unlock for travel)

If using Wi-Fi, yeah you can get apps for texting, calls, maps, etc. But, you do need to be on WiFi to send or receive, so only when you make the choice, someone calling or texting you will otherwise not get through. Maps and that can be downloaded and used offline, but search options for an address, or just "Restaurants near me", or other searches likely will not be available, unless you can "search" while you have wi-fi and save it.

I have since left ATT, moved to Google Fi. You might consider that. Buy a phone through them, then $20 a month for talk and text plus $10 per gig data. No foreign roaming charges, except obviously calling a number in Europe still is an International charge. Google Fi is now my primary, but if you want to keep ATT, it could be a good travel phone.

Another happy t-mobile customer here! It's so easy and stress free to travel abroad with t-mobile. The biggest stressor was believing that the perks were real! (They are)

Thanks Jean for the video link, that was really informative! Keri, it is well worth watching and will help with your concerns.

Am I correct remembering that texting still works with airplane mode 'on'?

No. In order to text, you have to be connected to the cell network wherever you are.

Getting a SIM card for each country has always seemed like a hassle (too many countries, too many cards). But this trip the countries are a bit fewer (mainly Spain, France, Italy).

As someone mentioned above, now a SIM card good in one European country works for all of them (since the EU eliminated roaming fees between countries on June 1, 2017).