WASHINGTON, Jan 13: The US military has grounded about one-quarter of its P-3 Orion aircraft fleet for inspections and repairs after the discovery of a structural fault, officials said.

The US Navy announced this week that due to a technical fault 39 out of a fleet of 161 P-3 Orions have been grounded. The Pentagon said the structural problem could cause cracks in the plane’s wings.

“The analysis and corrective measures are going to take between 18 and 24 months per aircraft to complete,” US Navy spokesman Lt. Clay Doss said. “The intention is to bring them back to the fleet.”

Pakistan has purchased seven upgraded ex-US Navy P-3C aircraft and ordered the upgrade of two Pakistan Navy aircraft. The upgrade includes Inverse Synthetic Aperture Radar, Electronic Support Measures and communication systems. The first was delivered in January 2007.

In late 2006, the US announced that it intended to sell three P-3C Orions equipped with the E-2C Hawkeye 2000 AEW system to the Pakistan Navy, along with 10 regular P-3Cs. The AEW aircraft will provide Pakistan with search surveillance and control capability for maritime operations.

Defence manufacturer Lockheed Martin’s Orion maritime patrol aircraft first went into service for the US Navy in 1962 and have been modified over the years, with the latest model built in 1990.