More mystery

On the Why Is It So? theme, I’m still wondering about something I saw a couple of weeks ago.

I was walking Minnie on the North Beach ovals at about 5pm and a group of kids pointed at the sky. I followed their gaze and saw a big jet, high enough to be leaving vapour trails. That’s pretty unusual in itself. We don’t usually see vapour trails around here. But this was a big, four engine jet, very high, leaving four, 2+2 lines, in the sky.

The odd thing is, it was flying NNW to SSE like this:
The thing is, why would a big jet be flying over Perth and not landing?

Planes don’t fly over Perth on their way to somewhere else, do they?

I admit I’m speaking from complete ignorance here. I know nothing about aviation and I’m sure there’s a valid reason, but I’m mystified. Where has it come from, why would it fly over Perth on its way to somewhere else on that sort of course? Surely the path to Adelaide, if that’s where it’s going, would be inland?

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