Three men went on trial in Paris on Monday over the bombing of a French military camp in Ivory Coast in 2004, which killed nine soldiers and sparked furious reprisals by the French, causing a deep rift in Franco-Ivorian relations.
But none of the suspects were present in court and their whereabouts are unknown.
Two Ivorian fighter jets were involved in the November 6, 2004 attack on French peacekeeping forces in Bouake, which was at the time in rebel-held territory.
Flying low, one of the planes fired rockets into the camp, killing nine soldiers and an American aid worker. Forty others were injured.
The attack came during an aerial offensive by then Ivorian president Laurent Gbagbo to try reclaim the country's north, which had been in rebel hands since 2002.
France reacted furiously, wiping out Ivory Coast's entire fleet of military aircraft, dealing a severe blow to Gbagbo's bid to end the rebellion.
Relations between France and its former colony, which had already been fraught, quickly deteriorated.
Violent anti-France protests broke out across the nationalist south.
France, fearing for the safety of its nationals in Ivory Coast, airlifted thousands of expatriates to safety.
- 'We want the truth' -
On Monday, one of two Belarussian mercenaries accused of carrying out the raid on the Bouake camp, Yury Sushkin, went on trial for murder, along with two Ivorian co-pilots, Ange Magloire Gnanduillet Attualy and Patrice Ouei.
All three were among crew members caught on camera after landing at an airport near the capital Yamoussoukro following the bombing raid.
If convicted they face a maximum term of life imprisonment, but as their whereabouts are unknown it is unlikely they will serve jail time in France.
Relatives of the victims are mainly hoping that the trial will provide clues about who ordered the attack on French forces and why.
Officials close to Gbagbo, who was toppled by French-backed rebel forces in 2011, claimed that the pilot mistook the French camp for rebel positions.
But some suspect it was a deliberate hit, aimed at clearing a path for Gbagbo's forces to storm rebel-held territory, or even that France itself masterminded the attack on its forces to have a pretext to try chase Gbagbo from power.
Among the many questions hanging over the affair is why France rejected an offer to have Sushkin handed over when he was arrested in Togo, which borders Ivory Coast, a few days after the airstrike.
"We want to learn the truth," the children of one of the victims of the attack, Philippe Capdeville, told AFP, adding: "The silence of French authorities on this affair is dramatic."