The World: The Men Who Watched The Planes Go By

Plane spotting, like collecting train numbers and automobile license plates, is one of those eccentric pastimes that the British love. Robert Curtis, 24, and Edward Paul Mason, 23, had been members of plane-spotting clubs since they were teenagers. In late September they took leave of their jobs in London and went to Yugoslavia. There they spent six days driving about the country, stopping at a dozen airfields to jot down registrations, types and numbers of all the aircraft they saw.

The two young hobbyists had almost completed their project when a Yugoslav civilian spotted them standing in the bushes outside a busy military airfield at Mostar, looking at the planes with binoculars. He called the police, who promptly arrested them and charged them with espionage. Curtis and Mason, police said, also had in their possession a large telescope, a shortwave radio capable of monitoring aircraft communications and a tape recorder. They also had several notebooks full of data about Yugoslavia's airfields, which were being used by Soviet planes to fly supplies to Syria and Egypt during the Middle East war.

Denying that there had been anything sinister about their activity, the two Britons insisted that they were innocently plane-spotting. "It's just a hobby, like collecting stamps or old coins," said Mason at his trial in Sarajevo last week. The Yugoslav judges were not persuaded. They found the two young Britons guilty of spying and sentenced them each to four years in prison.