The U.S. Navy has grounded 39 of its surveillance, anti-submarine planes due to concerns about possible structural failures in the wings.

Ten of the four-engine propeller planes are currently deployed overseas, and Navy spokesman Cmdr. Jeff Davis said they will return to the U.S. for repairs and it has not yet been determined how or if they will be replaced.

"We are acting early, based upon engineering analysis and fleet inspections, to ground these aircraft before a problem arises," said Davis.

The Navy has a total of 161 of the P-3C Orions, and their average age is 28. It will take 18-24 months to repair each of the planes, for a total of about three years to complete the process. Those that cannot be repaired will be pulled from service.

The Orions are some of the oldest aircraft the Navy has, and they are set to be replaced in coming years by the new P-8A Poseidon jet plane. The Poseidon are expected to be operational in the Navy fleet in 2019.

Davis said it is not clear yet whether the rest of the Orions will also have to eventually be taken out of service for repairs.

The 39 were chosen based on their age, number of hours flown and other computer analysis that showed they had exceeded the amount of fatigue on the wings that the Navy considered a concern.

The Naval Air Systems Command issued a bulletin announcing the grounding on Monday, saying it was determined that the 39 aircraft were "beyond known structural limits on the lower section" of the wing.