Commuters fled in "fear and panic" when a Tube train was engulfed by a "large fireball" at Parsons Green, a court heard.
Iraqi Ahmed Hassan, 18, is accused of planting a bomb on the District Line carriage during the morning rush hour on September 15 last year.
The Old Bailey heard the passengers were "fortunate" because it only partially exploded.
Prosecutor Alison Morgan told jurors: "On Friday 15 September shortly before 8.20am an improvised explosive device partially detonated on a District Line Tube train very shortly after it had arrived into Parsons Green Station. It was a rush hour and the train was crowded.
"There were approximately 93 people in the carriage when the device detonated. The partial explosion created a large fireball.
"Some in the carriage were caught by the flames and sustained significant burns.
"Many ran in fear and panic. They were fortunate. Had the device fully detonated, it is inevitable that serious injury and significant damage would have been caused within the carriage.
"Those in close proximity to the device may well have been killed."
Jurors were shown CCTV footage of the explosion.
Hassan, of Cavendish Road, Sunbury, Surrey, denies attempted murder and using the chemical compound TATP to cause an explosion that was likely to endanger life on September 15 last year.