The US said "regional extremists" could target the flights
The US 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".
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.
The AFP news agency reported that one plane en route to Juba was diverted as a precaution.
Uganda gay-rights activists are campaigning against the bill 
The top leadership body of Uganda's ruling National Resistance Movement (NRM) has endorsed President Yoweri Museveni as its candidate in the next election.
The opposition leader Hon. Maurice Ogenga Latigo (FDC vice president Gulu) survived death in a car crash. 
