About 20,000 Manchester United fans will descend on Stockholm for Wednesday night's Europa League final - more than half without tickets.
United were allocated only 9,500 tickets for the clash at the Friends Arena, with officials believing more than twice that number will head to the Swedish capital.
Concerns over potential flashpoints have been raised and an operation has been launched to keep the peace and supporters safe from the threat of a terror attack.
United fans with banning orders have been warned not to travel.