Wichita ? City and aircraft company officials are concerned that plenty of Wichita aircraft workers apparently are willing to move out of the state to find work.

Lockheed Martin and Northrop Grumman conducted a two-day job fair in Wichita, and hundreds of people lined up Wednesday and Thursday to apply for the jobs. The two firms plan to hire roughly 4,000 people this year to work on the Joint Strike Fighter, the next generation of strike aircraft weapons systems.

Lockheed has 1,100 openings in Fort Worth, Tex., 400 in Marietta, Ga., and 325 in Palmdale, Calif. The bulk of the jobs with Northrop Grumman are in California.

The fair comes as Wichita aircraft manufacturers are laying off thousands of workers. The manufacturers and other experts say the talented aviation workers who may leave the state could be hard to replace if production demand increases.

Two of those workers are Mark and Paula Trowbridge. Mark lost his job at Boeing Wichita in January. Paula, a sheet metal assembler at Boeing, will be laid off April 19.

The two, who have worked at Boeing more than five years, said they were willing to move.

“There’s not much out there,” Paula Trowbridge said of the Wichita job market.

“We’ve seen this happen before,” said Janet Harrah, director of Wichita State University’s Center for Economic Development and Business Research. In previous aviation manufacturing downturns, “we lose those skilled laborers.”

“When you have the inevitable upturn, we’ll have to go out and compete and try to lure those people back.”