It is a scenario that would send shivers down the spine of any parachutist.
Seconds after jumping from a military plane near Richmond Airport in Sydney, a paratrooper saw a Virgin Australia passenger jet flying at the same altitude to him just two kilometres away.
The paratrooper's account of the incident is contained in a report by air-safety investigators into a so-called "loss of separation" between an Army C212 plane and the Virgin Boeing 737 in November 2011.
A loss of separation occurs when two aircraft fly within 305 metres vertically and 9.26 kilometres on a horizontal axis of each other, raising the risk of collision.
At the time, the military turbo-prop aircraft had been carrying out two drops of paratroopers in controlled air space above a designated zone at the RAAF's airport at Richmond.
Shortly before the close shave, air-traffic controllers had cleared the Virgin passenger jet to fly under the C212 near Richmond on its way to Cairns.
The loss of separation occurred between the declared parachute operations area and the 737. The standard separation buffer around a declared parachute operations area is about 1.85 kilometres.
About 2.30pm on the day of the incident, an air-traffic controller cancelled the military plane's clearance to carry out parachute operations and told its pilots to maintain an altitude of 12,000 feet.
The controller told the pilots that a 737 was flying over Richmond at 10,000 feet, but was quickly told by the Army pilots several times that the paratroopers were "off the ramp" - they had already jumped out of the back.
Immediately afterwards, the controller issued a traffic alert to the pilots of the Virgin 737, telling them that "chutes [were] in the air".
Shortly afterwards, the Virgin pilots said they had the military plane in their sights and were turning right immediately. The Army pilots also told air-traffic control that they had sighted the Virgin jet and that it was well clear of the paratroopers.
One paratrooper reported seeing the Virgin jet pass an estimated 1000 feet below and 2000 metres towards the right rear of the military plane.
The last paratrooper to jump from the plane told investigators that, while in free fall, and about 10 seconds after exiting the C212, he was at the same altitude as the 737 and about two kilometres away.
In the report released today, the Australian Transport Safety Bureau found that Airservices Australia had "no standard, documented procedure" to ensure planes that had taken off from Sydney Airport did not fly too close to aircraft carrying out parachute drops near Richmond.
The country's civilian air-traffic control agency also did not have a "documented means" for controllers to display in their computer system when a parachute-drop clearance had been issued.
The air-safety investigators found that two controllers involved in directing the planes at the time of the incident had not received training in "compromised separation recovery techniques".
Airservices has since made changes to ensure co-ordination when parachute operations are being carried out at Richmond.
- Sydney Morning Herald