I’ve made hundreds of flight over the years with camping stoves in both carry-on and luggage — and only really had problems in New Zealand. They are VERY strict on all camping equipment, not wanting to introduce foreign pests.
But in 2021 I’ve had stoves questioned twice. The were not confiscated.
Friends had stoves taken and not returned!
Air Canada last week — for example — took my very clean JetBoil and had to have it approved by SOMEBODY before I could take it on the plane.
Here’s the Air Canada policy on that.
Here’s some advice from Backpacker magazine.
And some advice from CyclingAbout.
And advice from MSR.
I’m flying to Europe Nov 1, 2021 with a NEW camping stove in the box. In my carry-on.