Why is this plane flying a circular track?
A recent article in Aviation Week showed a modified Bombardier Global 6000 with a "canoe" type fairing underneath the fuselage which typically houses a variety of radar or electronic intelligence (ELINT) equipment (link (free registration req'd) with pic) (alternate). The UK's RAF flies the Sentinel aircraft which is based on a prior Bombardier model, the Global 5000. So it's certainly possible that the track is a valid orbit path for surveillance in that area.

The USAF E11A is based on a Global 6000. It carries the BACN battlefield communication relay system which allows integrated, real-time communication across several, sometimes incompatible platforms. It is designed to operate at high altitudes to allow coms over mountainous terrain. 

Since the Jalalabad airport is currently controlled by US armed forces from the adjacent Forward Operating Base Fenty, it would make sense that a communications aircraft would loiter over the area. 

If it is a military flight, it looks from the flight path that it may have originated from Kandahar, where the USAF has a base.


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