Essentially, it would be difficult (and expensive) to prove that PEDs will never interfere with critical nav equipment, so its easier and cost free to have them turned off for autolands.

New aircraft are shielded/tested to see if there are vulnerabilities with PED's. Kindof a snapshot in time, given 3G,4G, 5G, etc.

Airlines can have older aircraft tested, but why bother.

Anything built in the last 30 years has some level of HIRF protection (the requirements have evolved over time and are more defined and stringent on the newer stuff).
However, weird things still happen. There have been documented cases where the pilots experienced some flight deck anomalies and ask the FA to check who was using a PED and have them turn everything off - at which time everything returned to normal. What's really interesting is that they can never duplicate it later on - Boeing has gone as far as to purchase the actual PEDs from the passengers and test them and found nothing unusual.

During LVO all PED must be switched off.
On the A350 there is a switch in the overhead.
Safe flights to you all.

Depends. On my iPhone 6S+ (IOS 12.4.1) it only turns off cellular. On my iPad Mini 2 (IOS 12.4.4) it turns everything off.

I asked a similar question over on the Spectators Balcony a while back.
The replies were very informative.

I'm too new to link it here.
The title is Keeping Autoland "Current"?
A keyword search of titles only for:
Autoland
Will find it.

I had an interesting experience a long time ago, when starting to fly A320s. Back then, I had a Nokia Lumia Phone, which happens to be a Windows phone (it has been a while...). During one of my early line training flights on an old A320 with the legacy FMGC I obviously forgot to switch it off/to flight mode. Just before top of descend FMGC1 froze up, shortly afterwards followed by FMGC2. We reset the FMGCs and eventually recovered both of them. When coming back home after the rotation I noticed that my phone sent all messages that I have ever sent again (some people got quite confused when they got messages that were originally sent a couple of months ago...). At this point I didn't link these two occurrences, but a few months later I flew the same MSN and when I took my phone out to take some pictures during cruise the FMGCs started freezing. I guess there must have been a latent fault somewhere in the system that enabled the interference (as mentioned above it only happened on one MSN, but then we only had two aircraft in the fleet that still had the Legacy FMGC...).

I had never experienced this until today. Just landed ZRH on LX0345 and we too were requested to turn off all devices due to fog

Radio frequency, RF, interference can be a difficult thing to nail down. Sometimes it is easy: in a past life, I set up a radio transmitter at the BAFTA awards for the camera operators and the event host to hear the director, but when I switch it on, interference lines appear on the big picture monitors on the stage. Damn, my transmitter RF output is getting into the picture monitors. If I move the transmitter and aerial further away from the monitors, the interference will reduce or disappear.

Sometimes it is very difficult to track down. What can happen is that two devices transmitting on different frequencies can generate a third frequency, and the third frequency is the one that causes a problem.

Airbus aircraft have RF shielded cable looms, I assume modern Boeings do too. However, when flying auto-lands in low visibility conditions, we do so to much more critical and lower decision altitudes, say 22' or even no DA, so it is very important that the ILS receivers are not subjected to any interference and the aircraft is exactly in the centre of the ILS 'beams'.

So since it cannot be known whether every passenger transmitting device is actually benign, the safest solution is to switch all devices off completely - especially since even devices that are on receive only can nevertheless emit RF, owing to the way receivers work.

As has been mentioned, EFB's in the cockpit that can transmit data have to be tested and approved for not causing any interference.

I was able to generate spurious messages in our corp G-IV many years ago, admittedly over 30 years old and one of the earlier glass versions. These tests were not intended to validate (or not) RF interference, but to determine if voice encryption while airborne for the execs was at all feasible. At that time, the execs really only had laptops and early analog RF devices. Still, the chief pilot arranged a test and spent a couple of hours working with me because crews were already seeing odd messages appear - particularly disconcerting in ocean crossings and on approach (mentioned one incident descending into Rome in particular). SOP was to have the execs power everything off.
I brought two RF devices on board and could vary the strength of the RF signal with mods from Motorola. Of note, the higher the power output of the radio, the more frequent the faults occurred - but not always. Where I physically sat with the devices also made a difference - again but not always. There were some places in the aircraft where no faults appeared despite cranking the RF power to the max unless I shifted the oreientation of the device. There were other places where minimal power would start to generate messages regardless of orientation although less in number. If I repeated the same tests, I did not get the same results. Very un-scientific but enough that I shut my phone off without being told to do so on every flight after that.

This is SOP at my current airline in the US when conducting Cat II operations. As for our EFB's (ipad) - they are left on airplane mode.

Having read this thread, I played with my phone (iphone SE) and discovered that bluetooth was still ON in airplane mode. It seems the bluetooth switch overrides the flight mode.
So, by turning bluetooth on when it is in flight mode, it stays on regardless of flight mode selected or not. Turning bluetooth off in normal mode, it stays off no matter how many times you cycle modes.
If you put the phone into flight mode then turn the bluetooth off, bluetooth goes on and off as expected with the flight mode selection.
I had no idea this was happening and thought everything was shut down when I had it in flight mode!

One of the recent software updates introduced this behaviour. Now, if you turn Bluetooth off, it comes back on automatically the next day. I’m not a fan. I think WiFi follows the same logic.

Seems like some correlation going on there. Would be good if we could prove or disprove causation.

Same at my airline, I personally think it’s overkill but they pay the wages etc so who are we to argue?

Just for a data point: I just tried with my iPhone SE, iOS 13.3: was connected to my wifi and a Bluetooth device. When I turned on flight mode (Aeroplane Mode in Applespeak), the wifi went off but the Bluetooth stayed connected. That surprised me, as I thought flight mode cut out all transmissions. If it is a change in behaviour, would explain why an airline would get fussy when there's a genuine possibility of interference.

I would think that in any aircraft with 100+ pax, there will be at least one cell phone left operating for the entire flight. Pax boards goes to window seat pulls down blind (de-rigeur these days) straps in and goes to sleep phone operating. As far as I am aware no modern cell phones have been shown to interfere with aircraft systems: not the cellular signal, the WiFi, nor, the Bluetooth. It is not uncommon for the aircraft WiFi to be on at all stages of the flight (although the onward network connection to Internet may be offline) the aircraft base station is a LOT more powerful than a phone WiFi. I think that this is one of those rules like the ban that used to be applied on cell phone use at gas stations where nobody wants to be the first to say it is not necessary.

At the same time as the flight attendants are attempting to enforce a rule that has no safety impact, they are not asking for window blinds to be opened for taxi/takeoff and landing that does have a safety impact should an incident require a decision on what side NOT to evacuate from for example.

Correct, Also in flight mode the navigational mapping seems to work on Iphones showing where your flight is anywhere in the world. Obviously the phone must send out and receive signals when in flight mode to provide live navigational data.

Doesn't the GPS on a phone work even in flight mode ?