LIMA, PERU - Patricia Calvino has marked every day spent in a Peruvian prison on drug charges since 2013 with a cross through a calendar, a sobering reminder of how long she has spent away from her daughter in Spain.

Three years and seven months later, Calvino will join 30 other Spanish prisoners on Thursday on a flight back home - the largest repatriation of Spaniards serving prison sentences abroad in the European nation's history.

Peru is the world's second-largest cocaine producer, and much of the narcotics arriving in Europe passes through Spain, where traffickers prowl for recruits like Calvino in nightclubs, offering a hefty sum to travel to Lima and bring back cocaine.