Iran's media say at least one US fighter jet came dangerously close to an Iranian passenger plane in Syrian airspace - a claim denied by the US.
Iran's Irib state news agency says the pilot of the Mahan Air aircraft had to quickly change altitude, which resulted in injuries to several passengers.
But the US military later said its F-15 jet was at a safe distance.
"A US F-15 on a routine air mission in the vicinity of the at [al]-Tanf garrison in Syria conducted a standard visual inspection of a Mahan Air passenger airliner at a safe distance of approximately 1,000 metres [0.6 miles] from the airliner this evening," Capt Bill Urban, spokesman for US Central Command, said in a statement late on Thursday.
He said the inspection was carried out to ensure the safety of personnel at the US military base at al-Tanf, near the border with Iraq and Jordan.
"Once the F-15 pilot identified the aircraft as a Mahan Air passenger plane, the F-15 safely opened distance from the aircraft," the spokesman added.
The Mahan Air aircraft en route from Tehran to Beirut landed safely in the Lebanese capital.