A round rainbow is is better known as a glory, which isn't seen too often at ground level, but can be on occasions seen from a plane. You just need to get the right alignment of the sun (with the sun low in the sky), the plane, the weather, be sat on the correct side of the plane (opposite side from the sun) and be looking out just as you fly through the clouds to catch it.

With flying a lot now for a few years I've seen it quite a few times, but never really got a chance to get a good photo of it as the right conditions are normally before you get to 10,000 feet which is when on the Air NZ 737s you were not allowed to use electronic devices, however now on the A320s you are. This morning everything was lined up perfectly and I got this photo.
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What amazes me is that at the center of the glory is a silhouette which is that of the plane I was flying on in shadow. It looks even better in real life as the camera on a phone just doesn't quite do it justice.

For more about glories:

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Mike,

I've never seen that before.... Beautiful.

Peter.

If you climb behind Millaa Millaa Falls on the perfect day there are circular rainbows you can put your hand through and watch the colours climbing up your arm.

Only ever seen it twice but the pictures are still there in my mind.

Doing the same flight again on Monday morning, flying down to Wellington everything lined up again and I thought I was lucky enough to get another photo just after take off as we went through the cloud base.
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I thought the rest of the 45 minute flight was going to be as uneventful as it normally is until as we were approaching Wellington I spotted a "normal" rainbow, although it is clearly broken into two segments, no doubt due to a patch of cloud blocking the suns rays where the break was.
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That was the first time I've seen a "normal" rainbow from the air, so I thought I'd had the end of the special sights but then just before we landed I looked out and saw something I'd never seen before, this time a vertically aligned rainbow and it was a double one too!
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The photo doesn't really do it justice, it was even brighter and more prominent, but at least it gives you an idea of what it looked like.

Now see what happens next week!