An RAF C17 Globemaster transport plane, which had completed a nine-hour, 3500-mile journey from Brize Norton air base in Oxfordshire, arrived yesterday to find the runway at Juba airport blocked by a stricken Sudanese jet.
Briton Dave Stanley, who was waiting for evacuation, said the nose undercarriage of the Boeing 737 appeared to have collapsed, with the sound of an explosion as it landed shortly before the RAF aircraft's arrival.
UK nationals who had gathered at the airport after days of escalating gunfire in the South Sudanese capital saw the plane, which was supposed to take them to safety, circling above them, and were told at one point that it would have to call its mission off and return the following day.
But the Sudanese jet was eventually towed out of the way, allowing the pilot of the 266-tonne Globemaster to make what the Ministry of Defence described as a "daring, precision landing" on the cleared runway.
Mr Stanley, who was in South Sudan to set up a radio studio with the charity BBC Media Action, told Radio 4's Today programme: "It was chaotic, because we arrived at the airport before 10 o'clock in the morning and we had to wait to try to find out what was happening.
"One of the Sudanese airlines, Nova Air, came in with a flight - it may well have been a charter flight for evacuation - and on landing we heard an explosion and we subsequently saw the aircraft and the front landing gear had collapsed. Whether a tyre had burst or whether it was the collapse of the landing kit I don't know."
The commanding officer of the RAF's 99 Squadron, Wing Commander Stuart Lindsell, said: "I think it's fair to say this C17 captain and his crew have had one of the toughest days anyone on this squadron has had."