By Susy Solis, CBS 11 News

FORT WORTH (CBSDFW.COM) — The picket lines assembled at 12:01 this morning right outside the main gates at Lockheed Martin’s West Fort Worth Plant.

The Machinists Union, which represents 3,600 Lockheed Martin employees, rejected the company’s best and final contract offer in an overwhelming vote Sunday, then voted to go on strike.

Many members of the Machinists Union are aircraft assemblers or work in manufacturing functions at the plant. which produces F-16 and F-35 fighter jets.

The Machinists Union rejected the contract offer because of 2 issues: fewer and more expensive healthcare plan options and the elimination of a defined pension plan for new hires.

“Even though other corporations have cut them out, you know, why does Lockheed have to follow?” said Pauline Ramos, who has worked at Lockheed Martin for 31 years.

Husband and wife, Cory and Stephanie Shoe, say the fact that they both work at Lockheed Martin had no bearing on their decision to vote for a strike.

“We have to stand up,” said Stephanie Shoe. “I mean it’s now or never.”

Members of the Machinists Union had been warned for months to prepare for a possible work stoppage and plan accordingly.

The Shoe family said they saved their income tax return and began cutting back on other expenditures to prepare and save money.

“Each week, you know, we would take out X amount of money that we could afford,” Stephanie Shoe said.

Workers say Lockheed is playing hardball and they are prepared for a long strike. Many union members say they’ve saved enough money to last them months.

“Previously, our strikes have lasted about three weeks. I look for this strike to last longer,” Ramos said.

Ramos began her career at Lockheed assembling F-16 fighter jets. She’s been through four strikes with the company.

“Our forefathers fought for us, for what we have today, and we want to fight for the next generation that’s coming up.” Ramos said.

Meanwhile, Lockheed Martin has identified non-union employees who can perform the functions of the machinists. They will step in during the strike so the production of the F-35 jets won’t be delayed.

“We are disappointed that the union members rejected the company’s last, best and final offer and voted to strike,” said Joe Stout, a spokesman for Lockheed Martin, in a statement.

The company offered 3% annual general wage increases for the three-year contract, a $3,000 signing bonus, an annual $800 cost of living stipend and as well as an increase in pension payments for current workers.

But union members say they want affordable healthcare and a defined pension plan for new hires before they head back to work.

The Machinists Union members plan to picket outside various gates at Lockheed in four-hour shifts, 24 hours a day, until a compromise is reached.

So far, there has been no contact between parties. It is up to Lockheed Martin to reach out to union leaders to see when negotiations can resume.