The group of eight deny conspiring to blow up aircraft
The head of an alleged terrorist cell was seen looking up flight information shortly before being arrested, a court has heard.
Abdulla Ahmed Ali was watched by an undercover officer as he checked flight timetables in an internet cafe.
Woolwich Crown Court heard he also talked "in hushed tones" on his mobile.
Mr Ali and seven other men are on trial accused of conspiring to explode home-made liquid bombs on passenger jets in August 2006, which they deny.
Prosecutors say the men conspired to murder thousands of passengers by blowing up transatlantic aircraft destined for cities in the US and Canada.
Home-made liquid bombs disguised as Lucozade or Oasis drinks would be smuggled aboard before being detonated in mid-air, they said.
The court was told that Ali entered T&I Communications in Wood Street, Walthamstow, east London on August 6.
Prosecutor Richard Whittam said Mr Ali was observed speaking in "hushed tones in a foreign language" on a mobile phone.
Mr Ali was seen looking at the BAA Heathrow website showing "some sort" of timetable, before visiting a flight-booking website.
He was seen taking a second call in English, when he no longer whispered, referring to radios in boxes.
The court heard that he said: "Well, then take them out of the boxes... let me know about the weight."
Mr Ali was then seen looking at an American Airlines page marked "timetable notepad". He then highlighted sections of numbers on the screen.
The court also heard how on the same day, co-defendant Assad Sarwar, who was described as the group's "quartermaster", visited an internet cafe in Slough.
He was observed as he wrote an email and then made notes as he looked up internet sites related to hydroponics - the process of growing plants without soil. He also looked up information on plant growing and feeding.
Mr Sarwar was later seen using a public phone box to make calls to Mr Ali and co-defendant Mohammed Gulzar.
And in police surveillance footage, which was shown to the jury, the three men - Mr Ali, Mr Gulzar and Mr Sarwar - can be seen meeting in darkness in the evening of 6 August in Glenparke Road, east London.
The defendants are: Abdulla Ahmed Ali, 27, of Prospect Hill, Walthamstow; Assad Sarwar, 27, of Walton Drive, High Wycombe; and Tanvir Hussain, 27, of Leyton, east London.
Waheed Zaman, 23 and Arafat Waheed Khan, 26, - both from Walthamstow, east London - are also charged, as are Mohammed Gulzar, 26, of Barking, east London, Ibrahim Savant, 27, of Stoke Newington, north London, and Umar Islam, 29, of Plaistow, east London.
The trial continues.