PARIS (AP) — Loose papers left in the cockpit of an F-16 that crashed at a Spanish air base could have sent the fighter jet into its deadly spiral, French investigators have concluded.

The report released this week brings an end to a multinational investigation into what happened before the Greek plane's failed takeoff and crash in Albacete, Spain, on Jan. 26. The French military report found that papers left in the cabin, perhaps a checklist, likely shuffled shortly before takeoff, causing an "accidental modification" of the position of rudder controls that stabilize vertical motion.

The seemingly minor glitch seriously disrupted aerial navigation, hindering the attempted takeoff at the Los Llanos air base in southeastern Spain. The jet rolled to the right and 7.8 seconds later struck an aircraft parking area.

Both pilots and nine French servicemen on the ground died when the aircraft exploded into a fireball, and 21 people on the ground were injured, in what NATO called the worst crash during a NATO exercise in recent memory. The report emphasized that no country or individual could be held responsible.