The deal will likely be announced after the markets close on Monday or early on Tuesday, three people with knowledge of the development told Bloomberg News.
The sale amount would set a record for F-35s but would more than meet the Pentagon's years-long effort to drive down the cost per plane to $80 million. A $34 billion price tag would value each plane at $71 million.
The planes would go to both the U.S. and allies.
"It's a big positive for the company," Bloomberg Intelligence analyst Douglas Rothacker told the news service. "It's a huge show of support from the government that they're going to extend a contract of this size for their most important weapons program."
Morningstar analyst Keith Schoonmaker wrote in a report last week that "Lockheed's incumbent position, divestment of noncore businesses, and headcount reductions have enabled it to weather the [last] downturn in defense spending."
"The company has capitalized off a rebound in defense spending under the Trump administration, and we project at least 5% year-over-year growth in 2019 and 2020," he said.
Schoonmaker expects defense spending to continue rising. And "wide-moat Lockheed is well-positioned to capture this up cycle," he said, pegging Lockheed's fair value at $385.
He rates the stock three stars on a scale of five, which indicates it's fairly valued.
Lockheed Martin shares at last check traded at $372.30, up 0.4%, on a day the S&P 500 was up 0.65%.