The 28-year-old Argentina-born forward had been en route from Nantes in western France with pilot Ibbotson to make his debut for Welsh team Cardiff City when the plane disappeared over the English Channel on January 21.
AAIB said it was informed on Monday (January 28) that part of a seat cushion had been found on a beach near Surtainville on the Cotentin Peninsula in northern France. A second cushion was found in the same area later that day.
Rescuers scoured about 1,700 square miles (4,400 square km) after the single-engined Piper Malibu plane went missing but had failed to find a trace of the aircraft until Monday.
The plane had been cruising at 5,000 feet (1,525 m) when the pilot requested to descend to a lower altitude on passing Guernsey. It then lost radar contact at 2,300 feet (700 m).
The planned search area, which is based on the plane's last radar contact, is approximately 24 nautical miles north of Guernsey.