The F-35 jet fighter made its first flight Monday outside the U.S. at a military base in Italy. Reuters

The American-built F-35 fighter jet, the country’s most expensive defense procurement project at a cost of more than $1.5 trillion, made its first flight outside the U.S. Monday at an air base in Italy, a defense news report said. The one-hour, 22-minute flight of the Lockheed Martin-designed Joint Strike Fighter took place without any incidents and was a month ahead of schedule.

The much maligned aircraft rolled off the final assembly line and onto the tarmac at the Cameri Air Base, which is owned by the Italian government and operated by Italy’s Alenia Aermacchi, an Italian aerospace company, and Lockheed Martin. The base is the only facility outside the U.S. where the F-35 will be assembled and maintained.

The short flight was likely a confidence booster to the Pentagon and Lockheed Martin after years of problems with software, fuel tanks and various other components.

“As expected, the jet performed exceptionally well and without any surprises,” said Lockheed Martin test pilot Bill “Gigs” Gigliotti, who flew the aircraft.

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It’s not unusual for most defense projects to suffer from delays and problems with design, but the incredible expense behind the F-35 project, which is expected to produce around 2,500 aircraft through 2040, has raised big questions from Congress over funding for expensive military projects. John McCain, chairman of the Senate Armed Services Committee, has been a harsh critic of the aircraft during the last few years. McCain has accused officials of “cronyism” in the selection phase of the aircraft and complained the entire project raised serious concerns about how taxpayers’ money was being spent.

“The Joint Strike Fighter is the most expensive weapons system in history, and we must learn the lessons of past failures to ensure that taxpayer dollars are spent efficiently and American aviators can safely and effectively perform their missions. We owe them nothing less,” McCain said.

Italy’s first six F-35s are scheduled to be delivered by October 2016. Four more are expected to be delivered in 2017, four in 2018, seven in 2019 and 13 in 2020.

After the first batch is delivered, Italian pilots will commence initial pilot training at Luke Air Force base in Arizona.