The aircraft – a Chinook based at RAF Odiham in Hampshire – arrived in Jersey at around 11pm and departed for Southampton General a short time later.
It is not known if the incident was related to the Covid-19 crisis and in a statement the government has said they will not be releasing any more details to protect the confidentiality of the patient involved.
A spokesperson said: ‘Military assistance was sought for reasons of patient safety and to avoid any delay in the transport taking place.’