A fourth doctor has been charged over the suspected failed bomb attacks in London and at Glasgow airport.
Mohammed Asha was arrested on the M6
Dr Mohammed Asha, 26, has been charged with conspiracy to cause explosions and will appear at City of Westminster Magistrates' Court on Friday.
Dr Asha, from Newcastle-under-Lyme, Staffordshire, was arrested on the M6 motorway in Cheshire.
Four men have been charged and two men and a woman released without charge. One man is still being questioned.
Dr Asha is accused of conspiring with Bilal Talal Samad Abdullah, Kafeel Ahmed and "others unknown", Scotland Yard said.
He remains in custody at Paddington Green police station.
Last month, two cars containing petrol, gas cylinders and nails were discovered in London. A day later a burning car was driven into Glasgow airport.
On 6 July, Iraqi doctor Bilal Talal Samad Abdullah was charged with conspiracy to cause explosions. He was arrested at Glasgow airport following the suspected failed car bombing there.
On 14 July Australian police charged Mohammed Haneef, a 27-year-old Indian doctor, with providing "reckless support" to a terrorist organisation.
He was later granted bail of A$10,000 (£4,300) by a judge in Brisbane, but will remain behind bars under Australian immigration law.
Dr Sabeel Ahmed, 26 and from Liverpool, was charged on 14 July with not disclosing information that could have helped police arrest a suspected terrorist.
He is the brother of Kafeel Ahmed who was detained at Glasgow airport after the burning Jeep was driven into a terminal building.
He suffered burns to 90% of his body and remains in hospital under armed guard.
Two trainee doctors, aged 28 and 25, have been released without charge.
Both men were arrested at the Royal Alexandra Hospital, in Paisley, Scotland.