The Boeing 767, which can carry around 200 people, is at MoD Boscombe Down, a military base in Amesbury, Salisbury, ahead of its departure from an unspecified location on Tuesday evening.
Six people are currently expected to board the flight.
On Tuesday, more than 270 people were seen being brought ashore at Dover after crossing the Channel.
According to data compiled, it brings the total number of people crossing this year to more than 10,500.