Northern Lights in Iceland-

All of Iceland lies within the aurora zone. But for the best viewing chances, you need to be as far from the glare of Reykjavík's city lights as possible, on a clear night, during the right time of year with long periods of darkness (basically, winter), and during a solar storm. On any given night, the chances of seeing the lights are low, but the longer you stay, the greater you stack the odds in your favor.

For example, during a one month stay in Alaska during the winter, I saw the lights exactly three times, with multiple failed attempts, even on nights with a high prediction of aurora activity.

Spent five night in Iceland in October hoping to see the lights. The indications of activity were high but it rained every night and there was cloud cover.

It's hit or miss. You never know.

Yes, hit or miss. I've seen the Aurora while walking the dog in Spokane, had a great view during a camping trip in the Canadian Rockies, and seen them many times while flying through northern states for the Air Force. The Aurora is similar to rain, you can view the forecast and it's roughly as reliable. Add potential cloud cover and you may or may not see them. If you do see them you may be disappointed anyway. They are sometimes much more spectacular than others, getting away from city lights ups your chances of seeing them at their best.

Virtually all flights to Europe will fly very far north; the great circle route is the shortest even though it looks longer on a flat map projection. Make sure you get a window seat on the north side of the plane (left going to Europe, right coming home) and fly during the night and you may see them that way.