WASHINGTON (Reuters) - The Pentagon estimates it will cost nearly $16 billion to modernize the fleet of F-35 jets through 2024, a U.S. lawmaker said on Wednesday, citing information provided by the Pentagon on the stealth fighter jet program.

FILE PHOTO - A Lockheed Martin F-35 Lightning II fighter jet is seen in its hanger at Patuxent River Naval Air Station in Maryland October 28, 2015. REUTERS/Gary Cameron

The F-35, which is made by Lockheed Martin Corp, has been in production since 2006 and modernization expenses were expected. More than 270 of the jets are currently flying.

The F-35 has been widely criticized for being too expensive, including by President Donald Trump and other U.S. officials, who have also pointed to numerous production delays and cost overruns. Wednesday was the first time the $16 billion modernization estimate was made public.

Modernization costs would be split between $10.8 billion for software development and $5.4 billion for deploying the updates and other procurement in support of the modernization efforts, Representative Niki Tsongas said at a hearing of a subcommittee of the House of Representatives Armed Services Committee, citing the information provided by the Pentagon.

Vice Admiral Mathias Winter, the head of the F-35 Joint Program Office which administers the program, provided some detail on the modernization program.

“Continuous enhancements and improvements will be made to increase capabilities that make the F-35 more lethal and survivable,” Winter told the panel.

U.S. lawmakers and independent watchdogs are keeping tabs on the upgrade program after years of cost overruns and delays. U.S. officials said Lockheed Martin has made progress on cutting costs since a major restructuring of F-35 production in 2010.

The nearly $16 billion figure represented the outer limit of the modernization costs to bring all of the jets to their maximum potential currently known as “Block 4,” Winter told reporters after the hearing. The Pentagon was uncertain all F-35s would necessarily need to undergo this level of modernization.

International customers were estimated to be responsible for $3.7 billion of the $10.8 billion software development costs, with the United States shouldering the rest, spending about $1 billion per year over the seven-year plan, Winter said.

The costs would be for the more than 270 F-35 jets currently in the field and others that come off the production line in the near future.

Winter said he expected Lockheed to deliver 91 jets in 2018.

Lockheed and its partners, including Northrop Grumman Corp, United Technologies Corp’s Pratt & Whitney and BAE Systems Plc, have been working on building a more cost-effective supply chain.