Nearly 30 Mayors from across Florida, including Mayors from every major metro area, have signed onto a letter supporting the continued use of the F-35 Lightning II, which has faced criticism over software bugs and delayed upgrades.

The letter, sent to U.S. Sen. Rick Scott, highlights the fifth-generation fighter jets’ economic impact on the state, noting that “the presence of F-35 facilities and the associated supply chain” creates $21 billion in economic impact each year in Florida.

While criticisms have been leveled, the F-35, flown since 2006, is the cornerstone of the defense manufacturing industry, with a $72 billion economic impact across the U.S.

Florida’s economic impact related to the fighter jets represents a significant share of the impact nationwide. That’s largely due to Florida’s presence as a manufacturing hub for parts used in the aircraft.

The jets create a $7 billion economic impact in Orange County, supporting more than direct 1,800 jobs and more than 5,200 indirect jobs. Brevard County follows, with a $1.8 billion economic impact sustaining 6,400 direct jobs and more than 18,000 indirect jobs.

Elsewhere in the state, the impact is less profound, but still significant. Pinellas County sees an $88 million economic impact, while Seminole County enjoys an $87 million impact. Okaloosa County’s economic impact sits at $73 million.

“More than 170 Florida companies build parts for the F-35 and many of them are small and veteran-owned businesses” the Mayors point out in their letter.

While the fighter jets are assembled at a Lockheed Martin manufacturing facility in Fort Worth, Texas, more than 1,900 companies contribute to the jets, and most of the supply chain companies are small businesses.

Some 300,000 parts are manufactured at various plants, many in small towns, before the parts make their way to Texas for final assembly.

The parts are highly engineered and often complex assemblies with rigorous specifications. And that fuels jobs in skilled workforce trades, including engineering and machining, which draw talented graduates and craftsmen to jobs that pay well and spur economic activity.

“Local businesses, from restaurants and retail to housing and services, all benefit from the economic activity generated by the program’s presence,” the letter explains.

The manufactured parts that eventually make up the F-35 are what provide the fighter jets’ stealth capabilities and ability to share information from the battlefield in real time.

These design features have drawn 19 allies to partner with the United States to fly the F-35 and work collaboratively on the battlefield, making the F-35 a critical national security asset to many parts of the world.

Earlier this year Poland and Israel demonstrated the F-35’s prowess by repelling attempts by Russia and Iran to penetrate their respective airspaces.

“Supporting this program is an investment in our defense capabilities, which in turn protects our economic interests and ensures peace and stability,” the Mayors wrote.

They make the case that support for the F-35 must come from Congress in the form of increased procurement funding in the federal budget and vocal advocacy for the program.

“Support for the F-35 is intrinsically linked to the economic prosperity of our communities and the security of our nation,” the letter ends.

Signatories (in the order they are listed on the letter) include:

— Orlando Mayor Buddy Dyer.

— Crestview Mayor J.B. Whitten.

— Miami Mayor Francis Suarez.

— Melbourne Beach Mayor Alison Dennington.

— Tampa Mayor Jane Castor.

— St. Petersburg Mayor Ken Welch.

— Jacksonville Mayor Donna Deegan.

— Coral Gables Mayor Vince Lago.

— Cape Coral Mayor John Gunter.

— Doral Mayor Christi Fraga.

— Winter Springs Mayor Kevin McCann.

— West Miami Mayor Eric Diaz-Padron.

— Titusville Mayor Andrew Connors.

— Fort Lauderdale Mayor Dean Trantalis.

— Haines City Mayor Morris West.

— Panama City Mayor Allen Branch.

— Fort Myers Mayor Kevin Anderson.

— Apopka Mayor Bryan Nelson.

— Altamonte Springs Mayor Pat Bates.

— Homestead Mayor Steven Losner.

— Riviera Beach Mayor Doug Lawson.

— Panama City Beach Mayor Stuart Tettemer.

— Keystone Heights Mayor Nina Rodenroth.

— Niceville Mayor Daniel Henkel.

— Miami Lakes Mayor Joshua Dieguez.

— Fort Walton Beach Mayor Nic Allegretto.

— Hallandale Beach Mayor Joy Cooper.