Strong winter jet streams with winds up to 330 km/h are enabling eastbound aircraft to Melbourne and Sydney from Perth to shave up to an hour off flight times.

On August 15, a Qantas Boeing 747-400 flew Perth to Sydney in just 3 hours and 6 minutes, - essentially an hour better than the schedule of 4h 05min.

And on August 14 a Qantas A330 clipped 46 minutes off the scheduled 3h 30min flight time on the Perth to Melbourne route with an elapsed time of 2h 43min.

However, while some Perth bound flights have had extra long journeys for the same reason, sophisticated weather forecasting has enabled most flights to avoid the worst of the jet streams.

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See the jet stream graphic for Australia

The scheduled flight time from Sydney to Perth in winter is 5h 5min but most flights are beating that by around 15-20 minutes.

One exception was on August 15 when a Qantas Boeing 737 took 5h 44min to fly from Sydney to Perth.

There are four jet streams that circle the earth – two polar jets and two weaker sub-tropical jets.

It is the polar jet that impacts the east-west flight times and in winter sits broadly over Perth and in summer moves south over the Southern Ocean.

Jet streams, that bring the cold fronts, have been recorded at speeds of up 398km/h.

The polar jet stream is typically found at altitudes been 9000m and 12,000m.