A US MILITARY plane has been forced to return to Shannon Airport after experiencing an issue with one of its engines over the Atlantic.

The United States Navy Lockheed C-130T Hercules transport plane took off from Shannon at around 10.15am and was en route to the US via St John’s in Newfoundland, Canada.

About 30 minutes after departure, the flight crew advised air traffic controllers that they received a cockpit ‘indication’ which they were investigating.

The crew reported a problem with one of the aircraft’s four turbo-prop engines.

The flight had levelled off at 16,000 feet while the crew requested permission to deviate from their course so they could work on the problem.

They later sought clearance from controllers to descend to 10,000 feet so they could shut down and restart their engine to see if they could clear the indication.

The flight continued on course for a time but when the pilots couldn’t resolve the issue, they turned around to return to Shannon.

The crew had to dump aviation fuel to ensure they touched down within safe landing weight limits.

The crew did not declare an emergency and did not request priority clearance back to Shannon.

The flight returned to Shannon where it landed safely at around 12.15pm is expected to be inspected by engineers.

It was the second flight to make an unscheduled landing at Shannon today.

Earlier, an Aer Lingus flight from Dublin to Faro in Portugal turned back and diverted to Shannon after declaring a medical emergency.