The U.S. has been conducting intelligence-gathering flights over large parts of Nigeria since late November, according to flight tracking data and current and former U.S. officials, in a sign of increased security cooperation between the countries, Reuters reported. 

Reuters could not determine what information the flights are meant to obtain.

But the flights in West Africa follow U.S. President Donald Trump's threats in November to militarily intervene in Nigeria over what he says is its failure to stop violence targeting Christian communities. The flights also are occurring just months after a U.S. pilot working for a missionary agency was kidnapped in neighboring Niger, according to Reuters.