Two single-engine Cessna 208Bs planes were officially transferred to the Chadian air force in a ceremony at its base outside the capital N'Djamena.

The planes were delivered in December 2017 and have since been used for pilot training.

The US has also helped to build shelters and maintenance areas for Chadian aircraft, after a damaging windstorm in 2017 damaged air force facilities.

Together, the donated equipment and work amount to $43 million (36 million euros), said US ambassador Geeta Pasi, who attended the ceremony.

A vast, poor country in central-northern Africa, Chad is struggling with a jihadist insurgency that has spilled over from neighbouring Nigeria.

The country is allied with the United States in anti-terror operations, authorising the US military to have a drone unit, according to a Chadian military official.

However, relations were troubled last year when President Donald Trump unexpectedly slapped a travel ban on Chadian nationals -- one of six mainly Muslim countries to be so affected.

The ban on Chadians was to be lifted on April 13 after Chad "raised its security standards," the US Department of Homeland Security announced last month.

The former US secretary of state, Rex Tillerson, in a trip to N'Djamena in March, said Chad had made steps "to strengthen the control over its own passports, to strengthen the information-sharing".

On Monday, Trump, meeting visiting Nigerian President Muhammadu Buhari, said he was prepared to sell Nigeria helicopters in addition to a dozen A-29 Super Tucano light fighter aircraft as part of its anti-jihadism campaign.