United Airlines is closing shop in Nigeria from next month, citing weakness in the energy sector and difficulty in collecting money from tickets sold in the country.UNITED AIR

The airline currently operates a daily flight from Houston to Lagos, the carrier’s only route to Africa. The route has reportedly underachieved for years but has been kept alive because of its importance to Texas-based customers, United Continental Holdings Inc. said in a note to employees Wednesday.

The last flight will be June 30, after which Delta Air Lines Inc. will be the only major United States carrier flying to Africa. Nigeria has restricted the amount of money that can be moved abroad after the global slump in oil prices depleted the government’s U.S. currency reserves. The country owed airlines about $575 million in air fares as of March 31, according to the International Air Transport Association.

“Repatriation has been a significant issue, as has been the downturn in the energy sector,” said United spokesman, Jonathan Guerin, who confirmed the note’s authenticity.