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The Air New Zealand crew on board the ill-fated Airbus 320 were there to ensure the plane was in a good state before it was returned to New Zealand.
For the past two years it had been leased to German company XL Airlines and it is standard practice for such leased planes to undergo an "acceptance flight" before being returned to their owners.
Before the flight, the plane underwent ground and maintenance checks which it is believed to have passed without incident.
In the sky, it was then put through a series of manoeuvres to prove it met performance standards.
The German crew were still in control of the aircraft, which was flying under the German airline's register, but the New Zealanders were watching what was happening.
Air NZ chief executive Rob Fyfe said the role of the New Zealand team was to "observe the performance of the aircraft and to validate that it met Air NZ operating standards and the return policies requirements".
The acceptance flight had largely been completed and the jet was returning to Perpignan Airport in France when it plunged into the Mediterranean just before 4.30pm.
XL Airways Germany is a subsidiary of a European travel giant that collapsed in September.
Although the airline is reported to be trading as normal, its parent company, XL Leisure Group, entered into administration having suffered as a result of volatile fuel prices and the economic downturn.
XL's failure in Britain left a $200 million bill for the rescue of 85,000 travellers stranded abroad and 200,000 people demanding refunds for bookings.
During the northern summer the airline operated seven aircraft, including the Air New Zealand plane. They were used by several German tour operators to destinations in the Canary Islands, Turkey, Greece, Italy and Mallorca
In October, one of the airline's planes had to put down at Belgrade on a flight from Dusseldorf to Turkey after engine trouble was detected.
After landing, smoke seen from the left engine prompted an emergency evacuation but the airline later said there was no fire.
