The United States embassy in the Sudanese capital Khartoum has warned of a possible attack on Air Uganda planes.
The embassy said it had information that US travellers faced a potential threat between Juba in Sudan and the Ugandan capital, Kampala.
But the Sudanese foreign ministry said the threat was "not serious".
The BBC reports Sudan is on a list of 14 countries where US-bound passengers will be subjected to extra searches following the attempted plane bombing last month.
Other Sudanese officials said they had known of a potential threat for some time.
