Niger's coup leaders have closed the country's airspace until further notice, citing the threat of military intervention from their neighbours.
Flight tracking website Flightradar24 is showing that there are currently no aircraft in Niger's skies.
The West African group of countries, Ecowas, had earlier warned it could use force if President Mohamed Bazoum was not reinstated by 23:00 GMT on Sunday.
A junta spokesman says Niger's armed forces are ready to defend the country.
Mr Bazoum was detained on 26 July, and Gen Abdourahmane Tchiani, commander of the presidential guard, later proclaimed himself the new leader.
The military takeover has been internationally condemned, including by former colonial power France and the rest of the European Union, as well as the United Nations and the United States.
Reading a statement on national television on Sunday, the representative from Niger's junta said they had information that "a foreign power" was preparing to attack Niger.
After a crisis meeting in Nigeria, Ecowas military chiefs said on Friday they had drawn up a detailed plan for the possible use of force.
"All the elements that will go into any eventual intervention have been worked out here, including the resources needed, the how and when we are going deploy the force," said Abdel-Fatau Musah, Ecowas commissioner for political affairs, peace and security.
And he added: "We want diplomacy to work, and we want this message clearly transmitted to them [Niger's junta] that we are giving them every opportunity to reverse what they have done".
They issued their ultimatum a week ago, demanding the generals relinquish power by midnight local time, which has now passed.
Ecowas is a regional trading bloc of 15 West African countries, including Nigeria, Senegal, Togo and Ghana.
The coup leaders seem to be showing no sign of willingness to cede power, and on Sunday thousands of their supporters rallied defiantly at a stadium in Niger's capital Niamey.
Two of Niger's neighbours - Burkina Faso and Mali - earlier warned they would treat any outside military intervention in Niger as "a declaration of war" against them. Burkina Faso and Mali are both Ecowas members but have been suspended from the bloc since being ruled by military juntas.
Niger is a significant uranium producer - a fuel that is vital for nuclear power - and under Mr Bazoum was a key Western ally in the fight against Islamist militants in West Africa's Sahel region.
Niger coup: The basics:
Where is Niger? It's a vast country in West Africa, and one of the poorest countries in the world.
Why was there a coup? The military said it seized power because of insecurity and the economic situation, but there have been suggestions it came after reports the coup leader was about to be sacked.
What next? It's feared the military may seek to switch allegiance to Russia and close French and US bases there; for their part, Niger's neighbours have threatened to use force to end the coup.
Source: BBC
