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I was on the flight CX635 from Hong Kong to Singapore today, and I noticed the plane turning in a circle reminiscent of the holding pattern that planes often enter when they are queuing up to land.

However, this time I saw this flight pattern on the in-flight tracker while it was still in level flight, and once again when it was descending. When I got home, I saw that the pattern was also recorded on FlightRadar24.

enter image description here

Why did the pilot fly two circles in the middle of the ocean off the east coast of West Malaysia? I did not observe any obvious severe weather patterns, and the clouds were generally sparse (2 oktas or so) when it was doing the first roundabout, and there were no visible indicators of significant severe weather activity.

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    $\begingroup$ Running ahead of schedule for landing? $\endgroup$ – SF. May 25 '16 at 13:08
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    $\begingroup$ @SF. While that is plausible, the flight landed 8 minutes late, and furthermore from my experience, they usually do the circling near the airport if they are unable to be cleared to land immediately, and this is the first time I have seen planes circle while nowhere near the airport. $\endgroup$ – March Ho May 25 '16 at 13:20
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    $\begingroup$ @MarchHo "near" is relative when speaking of aircraft travelling at hundreds of knots. $\endgroup$ – Federico♦ May 25 '16 at 13:23
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    $\begingroup$ Having holding patterns that far out from the airport are not uncommon. It's not usually so much a matter of the aircraft being 'early' relative to its published schedule, but rather the destination airport being busy and them not being sequenced for landing as early as they'd hoped. Since the plane can't just stop to wait for its turn in the sequence, it has to fly a holding pattern. Also, like Federico mentioned, 'far' is a relative term here. 150 miles (approximately the distance here) is only about 15-20 minutes at the speed of an airliner. $\endgroup$ – reirab May 25 '16 at 13:57
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    $\begingroup$ Wow, quasi-perfect holding pattern! $\endgroup$ – mins May 25 '16 at 17:40
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The first "circle" is a holding pattern. We discussed those here. In particular, it seems that you were on hold at VINIL or VEPLI, according to the approach charts (page 5 of the PDF).

The second one is most likely for separation on final approach, the aircraft was probably early and ATC has asked them to perform a 360° to increase the separation between them and the aircraft in front.

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    $\begingroup$ Great answer. It's interesting how inefficient the system is, in regards to fuel consumption. The first circle is not that long after takeoff. I wonder if the destination airport knew about the congestion before the flight even departed. Maybe the originating airport wanted the space, or perhaps the airline didn't want a history of late flight departures, so they left on time, but then flew around in circles as directed by ATC. They obviously wasted a fair amount of fuel. As a side note: The map does not reveal if they performed the circle/oval patterns once or more than once. $\endgroup$ – RockPaperLizard May 25 '16 at 18:48
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    $\begingroup$ @RockPaperLizard, those circles are as the plane was coming in to the destination (Singapore), not leaving the originating airport (Hong Kong). $\endgroup$ – JPhi1618 May 25 '16 at 19:09
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    $\begingroup$ @JPhi1618 Thanks! I was holding the map upside down. ;-) $\endgroup$ – RockPaperLizard May 26 '16 at 6:12

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