A jury at London's Kingston Crown Court found Junead Khan guilty of preparing an act of terrorism.
The 25-year-old's work for a pharmaceutical firm took him past several US air bases in eastern England, and prosecutors said he discussed ways of targeting them with an IS militant in Syria.
Prosecutors said Khan, who was arrested in July, had exchanged online messages with a man calling himself Abu Hussain. They discussed attacking military personnel after faking a road accident.
In one exchange, Khan told Hussain he had seen some soldiers driving, "but I had nothing on me or wouldve (sic) got into an accident with them and made them get out the car." Hussain replied: "That's what the brother done with Lee Rigby." Rigby was a British soldier who was run down by a car and stabbed to death by two al-Qaida-inspired attackers in 2013.
When police raided Khan's home, they found an IS-style black flag and a laptop containing an article from an al-Qaida magazine entitled "Make a bomb in the kitchen of your mom."
Both men will be sentenced May 13. Junead Khan faces a maximum sentence of life in prison.
