Northrop Grumman Corp. officials would like to inspect Plant 5 in Bethpage, where the lunar landing modules that took astronauts to the moon 40 years ago were built by the old Grumman Corp., to see whether it could be used for an anniversary celebration in July of that historic event. But there's one problem: Angelina Jolie is at work in Plant 5. No, she's not building spacecraft. The actress and a crew are using the old Plant 5 to film "Salt,'' a spy flick. "We wanted to see if we could do anything with the old building" to help mark the anniversary of the moon landing July 20, 1969, Dianne Baumert-Moyik, a Northrop Grumman spokeswoman, said last week. "But we didn't want to interrupt the filming." Jolie and the film crew have been working at Plant 5 for three months, Baumert-Moyik said, and may be there a few more months yet. The situation has created something of a quandary for Northrop Grumman, the Los Angeles-based aerospace and defense company that maintains a major facility in Bethpage. The company no longer owns Plant 5, having sold it to Nassau County, which in turn sold it to an East Setauket-based developer, who has named the building Lunar Module Park Llc. So the company can't exactly barge in. On the other hand, Plant 5 would make a superb spot for the anniversary. It's where engineers and technicians at Grumman - which was acquired by Northrop Corp. in 1994 - toiled for years building the lunar excursion modules. The LEM, as it was known, took astronauts Neil Armstrong and "Buzz" Aldrin to the surface of the moon. A spokeswoman for the film said Northrop Grumman had not contacted them about entering the plant. "This is the first we've heard of it," she said. "Have Northrop Grumman contact us." No matter what happens with Plant 5, Northrop Grumman is making plans for the anniversary at the Cradle of Aviation Museum in East Garden City, Baumert-Moyik said. One topic sure to be discussed during the anniversary will be Northrop Grumman's role in the next mission to the moon. Northrop Grumman is among several companies that have won NASA contracts to develop designs for a new lunar lander. NASA is developing plans to return to the moon by 2020. The space agency's Constellation Program calls for a new generation of spacecraft, including the Altair lunar lander. Northrop Grumman is hoping its experience in building the first lander will give it a leg up in the competition.