WASHINGTON, United States– An Atlas Air Boeing 747 cargo plane made an emergency return to Miami International Airport following an engine problem shortly after takeoff, the airline said -- prompting another investigation into the aviation giant.

The plane, which was headed to Puerto Rico, landed safely late Thursday "after experiencing an engine malfunction soon after departure," an Atlas Air spokesperson told AFP in a statement. No injuries were reported.

"The crew followed all standard procedures and safely returned to MIA," the spokesperson said, adding that the airline would investigate the cause of the incident.

A post-flight inspection revealed a softball-size hole above the second engine, said the Federal Aviation Administration (FAA) in a notice.

The National Transportation Safety Board told AFP that it has opened an investigation into the case.

Boeing said in a separate statement that it is supporting its customers and will aid with the NTSB review.

The plane uses four engines made by GE Aerospace, which is also providing technical assistance as investigations proceed.

Atlas Air, which started operations in 1992, said on its website that it runs the world's biggest fleet of Boeing 747 freighter aircraft.

- Heightened scrutiny -

US aviation giant Boeing is under intense global scrutiny over its 737 MAX 9 jet, following a scare on an Alaska Airlines plane this month when a panel came off mid-flight and forced an emergency landing.

There were no fatalities or serious injuries in that case either, but US regulators grounded 171 MAX 9 planes with the same configuration as the jet involved in the incident.

Boeing shares took a hit earlier in the month, with the FAA launching a safety probe into the January 5 Alaska Airlines incident too.

The FAA said this week that its probe would extend to Boeing's manufacturing practices and production lines.

This was the first major in-flight safety issue on a Boeing plane since two fatal 737 MAX crashes, one in 2018 and one in 2019, led to a nearly two-year grounding of the aircraft.

Several incidents involving Boeing planes have since garnered attention, with an All Nippon Airways flight reportedly having to turn back on Saturday after a crack was found on the cockpit window of the Boeing 737-800.

On Wednesday, US Secretary of State Antony Blinken was forced to delay his return from Switzerland due to what a US official called a "critical failure" of his airplane, also a Boeing.

A separate plane was sent to retrieve Blinken, with aides returning to Washington by commercial flight.

While US air safety regulators have completed inspections on 40 grounded 737 MAX planes, they have not specified when the aircraft would be cleared to return to service.