* Fifty U.S.-built planes will eventually arrive in Israel
* Event overshadowed by Trump criticism of F-35 project cost
* Aircraft cost around $100m each
By Ori Lewis
NEVATIM AIR BASE, Israel, Dec 12 (Reuters) - - The much-hyped arrival in Israel of its first two U.S.-built F-35 fighter jets was heavily disrupted on Monday after bad weather delayed their take-off from Italy.
The delay - plus U.S. President-elect Donald Trump's complaints on Twitter that Lockheed Martin's whole F-35 project was far too expensive - overshadowed what was a day of celebration in Israel.
The ceremony was pushed back until after nightfall at the Nevatim air base in the southern Negev desert. It was due to be attended by Israeli Prime Minister Benjamin Netanyahu and U.S. Defense Secretary Ash Carter.
Israel's F-35 squadron is expected to be the first to be operational outside the United States and will enhance its ability to attack distant targets using stealth. The two planes will be the first of 50 fighters, each priced at around $100 million, Israel's air force will receive.
A U.S. squadron of the planes, which have encountered many delays and cost overruns, become operational in August. The F-35 program is the Pentagon's largest weapons project.
"The F-35 program and cost is out of control," Trump said on Twitter, sending Lockheed Martin's shares down 4 percent.
Asked about Trump's criticism, Jeff Babione, Lockheed Martin's F-35 program leader, said the company understood concerns about affordability and had invested millions of dollars to try to reduce the jet's price.
Israel, which finalised a 10-year, $38 billion package of defence assistance from the United States this year, plans to maintain two F-35 squadrons after it receives all the aircraft it has ordered.
Critics of the plane have said it can carry a smaller weapons payload and has a shorter range than Israel's current battle-tested squadrons of U.S. built F-15s and F-16s.
But some experts say the F-35's stealth capabilities make up for this because it can be more accurate and can fly a more direct route to its potential target. Israel's air force mostly flies missions close to home, in the Gaza Strip and against arms shipments to Hezbollah guerrillas in Lebanon and Syria.
It also is widely believed to have carried out bombings in Sudan against arms shipments to Palestinian militants, and to have drawn up contingency plans against Iranian nuclear facilities.
Israel initially ordered 33 of the fighters but signed off on another 17 last month.
Nimrod Shefer, a retired Israeli air force major-general, told reporters the new aircraft would be a welcome addition in ever more challenging and diverse battlefield environments.
"(There are) very low- to very high-altitude missiles ... and targets that are becoming more and more difficult to detect and to destroy," said Shefer. (Writing by Ori Lewis and Maayan Lubell; Editing by Jeffrey Heller and Alison Williams)