All NATO pilots taking part in the `Cooperative Key 2001` exercises in Plovdiv have been placed under stepped up security measures. Cordons of gendarmery and police armed with automatic rifles have sealed off all the sites where the pilots work and sleep. The access of outsiders to the `Plovdiv` Novotel, where most of the 260 US military have been accommodated, is prohibited. All entrances and fences of the 5-star hotel are heavily guarded. Only the hotel personnel is allowed inside but after a thorough checkup of their ID cards and luggage. `There is no panic among the Americans. During the breaks they drink coffee in the foyers and comment on the situation. However, they are not allowed to leave the hotel, personnel sources explained. The air bases at Graf Ignatievo and Kroumovo have also been blocked by the military police. This is the largest-scale exercise of NATO in Europe and is also likely to become a target of terrorist attacks, participants announced.