Two men have been remanded in custody after appearing in court accused of a part in an alleged plot to blow up transatlantic airliners in mid-flight.
Seventeen people have now been charged over the alleged plot
Don Stewart Whyte, 20, of High Wycombe, Bucks, and Mohammed Usman Saddique, 24, of Walthamstow, east London, are accused of preparing acts of terrorism.
Mr Stewart Whyte also faces three firearms charges.
They were remanded by City of Westminster magistrates to appear at the Old Bailey on 18 September.
The pair, both wearing white T-shirts and with short dark hair and beards, spoke only to confirm basic details about their identity during the brief hearing.
A bail application on behalf of Mr Saddique was refused, while there was no bail application on behalf of Mr Stewart Whyte.
Seventeen people have now been charged following arrests made in August.
Mr Stewart Whyte and Mr Saddique were charged by officers at Belgravia police station in London.
The terrorism charge against both men alleges that between 1 January and 10 August 2006, with the intention of committing acts of terrorism, they were preparing to smuggle parts of improvised explosive devices onto aircraft and assemble and detonate them on board.
The firearms charges against Mr Stewart Whyte allege that on 9 August he had in his possession a Baikal 8mm pistol.
He is also charged with possessing a magazine clip with 10 rounds of ammunition and possessing a black gun silencer without holding a firearms certificate.
Three others being questioned over the alleged plot have been released without charge.
The plot is alleged to have involved smuggling improvised explosives onto US-bound jets from London, where they would have been assembled and detonated on board.