Bluetooth Headset - Do I have anything to worry about if I don't use it during the flight?

Yes, they are allowed to carry them on. They will be treated like every other electronic device at the terminal entrance (screening).

In the US and my many experiences at LHR, these would not qualify as a 'large electronic device' which is laptops, game consoles etc. You can leave them in your bag unless specifically asked to remove 'any electronic device' which I personally have never seen or heard happen.

You should check with your specific airline as to whether they allowed in flight as different airlines have different policies on wireless devices if you do choose to use them.

There's no reason at all that you can't take these on the plane. If there's some specific thing you're worried about, it might be one of the following.

• Restrictions on the use of wireless devices on planes. You might be asked not to use wireless devices during take-off and landing; it's fine to use something like Bluetooth during the rest of the flight, since it's a very low-power signal. Many flights now have wifi in the cabin, for example. Note that you're not allowed to use your cellphone's cellular service on flights, but it's never been forbidden to bring the phone itself into the cabin.

• Restrictions on lithium batteries. The batteries in your headphones aren't nearly high-enough capacity to cause issues, here. They only start to kick in with unusually large laptop batteries, powerbanks and the batteries that come in devices such as mobility scooters and hoverboards.

Indeed, you have nothing to worry about even if you do want to use the headset during the flight. This article from USA Today is primarily aimed at the American market but gives non-US examples of airlines allowing bluetooth during cruise.

I have no intention of using them during the flight itself as I prefer listening to all the plane noises.

I'm guessing you don't fly much and possibly haven't flown before? 🙂

Honestly, the "plane noises" are mostly just loud-ish white noise from the constant drone of the engines and the constant whoosh of air past the plane. Especially during cruise, there really is nothing worth hearing. For hour after hour. Sure, during take-off and landing, there's a little bit to hear (the change in power from the engines, the gear being raised and lowered and so on) but in cruise, there's nothing. I find that, after a transatlantic flight I arrive feeling much fresher if I've used noise-cancelling headphones to dramatically reduce the volume of noise in the cabin.

I (and many other travellers) regularly wear battery-powered bluetooth headphones on flights out of Heathrow (and many other airports). If you take a look around the cabin on any longhaul flight you will see numerous people wearing QC-35s.

These kinds of premium noise cancelling headphones are specifically designed for air travel.

If you want to be sure you can cross reference the size of the internal battery (if it's a lithium ion battery) with the maximum permitted lithium ion battery, but it's going to be far less than a laptop battery (and laptop batteries are typically close to the upper limit permitted). What security worries about with battery sizes is those large external battery packs; small devices with batteries in them do not get a lot of scrutiny. Other things to be cautious about with electronics is if you've modified the electronics in any obvious way, or if you have wires sticking out, security doesn't like that sort of thing.

For the best security experience, put your electronic devices separately on the tray --- at Heathrow they can stay in their cases but it's a good idea to put electronics apart from each other, with a bit of space, flat on the tray (not stacked atop each other or deep in a bag mixed with chargers and other wiring), so that on the xray it's easy to see what the individual electronic items are. If you need to use more trays, that's better than trying to squeeze everything onto one tray and the xray operator getting confused.