Jet engine supplier Pratt and Whitney confirmed yesterday that it stopped production of F135 engines slated for the F-35 Lightning II for a three-week period in May of 2014 after an issue with a titanium supplier."Suspension of F135 engine deliveries due to the A&P Alloys issue lasted approximately three weeks," Pratt & Whitney spokesman Matthew Bates told IHS Jane's. " We were not able to validate the pedigree of the material as required ."The issue is particularly notable, Jane's points out, due to the June engine fire in an F-35 at Florida's Eglin Air Force Base. The fire is apparently "unrelated" to the titanium part, although that hasn't stopped the Air Force from holding off on engine deliveries "until further notice." The investigation into the June fire is still ongoing, Jane's reports.The heart of the May issue rested with the fan variable arm. Over 100 aircraft were fitted with the sub-standard part, with replacements to be installed using funds from Pratt and Whitney's pocket.