Nine years ago, just before the Obama administration pulled the plug on a troop presence in Iraq, Baghdad signed a landmark $4.3 billion, U.S.-backed Lockheed Martin deal to bolster its burgeoning air force with its very own fleet of F-16 fighter jets. The first batch arrived three years later, under the guise that the force would stand on its own two feet.

But billions of dollars and almost a decade later, some Iraqi pilots tell Fox News that there is little left of their investment and they fear few pilots are combat-ready to take on another ISIS wave or emerging threat.

So, what is going on?

Even before the global coronavirus pandemic swept through the beleaguered country, the Iraqi military was on high alert after the Jan. 3 U.S. assassination of Iran's top commander, Gen. Qassem Soleimani, as he touched down in Baghdad. Retaliatory missile strikes against two U.S. bases resulted in the U.S. withdrawing some contractors and troops from an array of locations -- including the F-16 homestead, Balad Airbase, just north of the capital.

An F-16CM Fighting Falcon, flown by U.S. Air Force Maj. Craig Baker, Air Combat Command Viper Demo Team pilot, flies through the air during a demonstration practice at Shaw Air Force Base, S.C., Jan. 15, 2016. Baker flies to demonstrate the combat capabilities of the F-16, similar to the tactics used while the F-16s are deployed. (U.S. Air Force photo by Airman 1st Class Destinee Dougherty)

An F-16CM Fighting Falcon, flown by U.S. Air Force Maj. Craig Baker, Air Combat Command Viper Demo Team pilot, flies through the air during a demonstration practice at Shaw Air Force Base, S.C., Jan. 15, 2016. Baker flies to demonstrate the combat capabilities of the F-16, similar to the tactics used while the F-16s are deployed. (U.S. Air Force photo by Airman 1st Class Destinee Dougherty)

Lockheed Martin contractors withdrew from the base between Jan. 4 and 8, after enduring indirect rocket fire from Iran-backed militias, the Pentagon confirmed at the time.

But according to two Iraqi Air Force pilots, who spoke on the condition of anonymity as they were not authorized to speak on the record, issues have emerged over the past months.

"The issue is Lockheed withdrew its employees. However, all these planes [F-16s] need to be serviced and supervised," one source said. "But because of a lack of parts, the Iraqi defense ministry started making its own parts and things, which is not allowed and effectively voids the warranty on them. In one case, a tool was left inside one of the engines."

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The Iraqi pilot claimed that "most planes are now grounded because they [air force personnel] don't know what they are doing re the upkeeping, which in turn means that the Iraqi pilots can't do their certification flights every month thus are rendered not combat-ready."

Another Iraqi military analyst framed the alleged situation as especially concerning, given that the F-16s are "essentially their strongest weapon against ISIS," which still frequently carries out attacks across its collapsed "caliphate" spawning Iraq and Syria.

"We used to fly 16 sorties [a takeoff mission] a day with two jets standby for combat. But now only two-[to-]four sorties a day if we even get airborne. This is due to the lack of proper maintenance and spare parts for the airplanes," a second pilot continued. "So much wasted money. The planes are poorly maintained; it went from 18 to 20 airplanes fully combat-capable to only seven now."

The insider also underscored that while the controversial Iranian-supported militias -- known as the Popular Mobilization Forces (PMFs) and adverse to the U.S and its allies -- have not made use of the F-16s, the fear remains that with little American footprint on the ground, "there would be little to stop them" going forward.

PMF units have, in years past, taken the helm of American-made Iraqi M1 Abrams tanks.

In this Feb. 13, 2018 file photo, an Iraqi army soldier stand guard near a U.S.- made Iraqi Air Force F-16 fighter jet at the Balad Air Base, Iraq. Iraqi security officials said on Jan. 12, 2020, four members of Iraq's military have been wounded by a rocket attack targeting Balad Air Base, an air base just north of Baghdad. American trainers and a company that services F-16 aircraft are present at that base. Sunday's attack by at least six rockets came just days after Iran fired ballistic missiles at two bases in Iraq housing U.S. forces, causing no casualties. (AP Photo/Khalid Mohammed)

In this Feb. 13, 2018 file photo, an Iraqi army soldier stand guard near a U.S.- made Iraqi Air Force F-16 fighter jet at the Balad Air Base, Iraq. Iraqi security officials said on Jan. 12, 2020, four members of Iraq's military have been wounded by a rocket attack targeting Balad Air Base, an air base just north of Baghdad. American trainers and a company that services F-16 aircraft are present at that base. Sunday's attack by at least six rockets came just days after Iran fired ballistic missiles at two bases in Iraq housing U.S. forces, causing no casualties. (AP Photo/Khalid Mohammed)

Similar concerns over the F-16s were raised earlier this month by the Iraqi Oil Report, which stressed that the apparent "grounded jets serve as a prime example of expensive U.S. military assistance that has failed to create a meaningful Iraqi military capacity."

Part of the roughly $300 million per year purchase agreement, according to the Iraqi Oil Report analysis, was that Lockheed engineers would "maintain the fleet of fighter jets." The agreement also stipulated that mission equipment and a support package [would be] provided by Lockheed and other companies."

While Fox News could not verify the claims made by the Iraqi pilots, and the numbers provided as to how many of the bomber jets are ready to fight, a U.S. government official said that Lockheed Martin is still working with the Iraqi air force and servicing the F-16s and that the Pentagon was "not aware of Iraqis making their own parts for the program."

"The security assistance enterprise has been working diligently with our Iraqi partners to support their F-16 program," the official said.

And in a statement to Fox News, a spokesperson for Lockheed Martin also emphasized that the company "values the relationship and partnership we have with the Iraqi Air Force," and referred further questions to Baghdad officials.

Iraq's Ministry of Defense (MOD) has dismissed claims of fatal flaws in the F-16 accord.

"The F-16 jets continue to fly for training and combat missions even after the withdrawal of the American companies," the ministry said in a statement posted on Facebook last month, muddying the extent to which Lockheed is indeed working with Iraq on the ground, but highlighting that the "Iraqi expertise that has the proven ability to maintain these modern jets, having completed technical workshops at different levels."

A spokesperson for the Iraqi air force additionally told Fox News last week that its top commander had just returned from a visit to Balad Airbase, insisting that there were 19 F-16s, "all of them in good condition" and now reliant on Iraqi technicians and experience, but it was hopeful that Lockheed employees would "return to Iraq very soon."

Moreover, a recent Rudaw article reported that Maj. Gen. Tahsin Khafaji, spokesperson of the Iraqi Joint Operations Command, told Iraqi state media that all the jets are "in good condition," insisting that "Iraqi F-16 fighter jets will continue to target the ISIS remnants, as the jets are all in good condition. Iraqi technicians are constantly working on maintaining the F-16 jets to continue their work targeting ISIS terrorists."

But the denial of problems, according to several Iraqis on the ground, is an immense source of frustration and concern for those tasked with being in the line of fire.

"The longer there are no contractors, the worse it is going to get," the Iraqi military analyst surmised.

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As early as January this year, concerns were percolating that the Iraqi F-16s "could be in jeopardy" as conflict with Iran reached fever pitch. According to Foreign Policy magazine, the supposed "gesture of goodwill and a good-faith effort to give Iraq the military it needed to defend itself against regional adversaries like Iran and the Islamic State [ISIS]," had turned sour with both U.S. and Iraqi officials expressing a growing concern that the fleet was "vulnerable to seizure by Iranian-backed militias."

"Since the contractors left Balad, some officials are concerned that the weapons, technology, and components associated with the F-16s could be vulnerable," Foreign Policy wrote, citing a former Iraqi F-16 pilot who also lamented that the Iraqi soldiers on base were not being given adequate food, rest and were operating on "a rotating schedule, with one week on base and one week off so they can seek employment elsewhere, causing potential operations gaps."

Reports have also pointed to Balad Air Force as a prominent point of corruption in the Iraqi military apparatus, ranging from schemes to steal fuel to smuggle on the black market, to Sallyport Security personnel on base becoming embroiled in alcohol smuggling and human trafficking endeavors -- all of which contribute to the calamity and hinder the readiness of pilots in the hot zone.

Having not had much in the way of an air force in the aftermath of the 2003 U.S.-led invasion of Iraq and the toppling of dictator Saddam Hussein, the new Iraqi government first put the steps in motion in 2008 to buy 36 advanced F-16s, the most sophisticated system it could add to its arsenal, at the height and surge of the Iraqi war. The first order was made in 2011, and a second in 2012, with the intention to aid an American withdrawal and empower Iraq to be able to defend its own borders. The delivery came in June 2014 -- just days before a then little-known terrorist outfit named ISIS took sudden control of the country's second-largest city, Mosul, before going on to annex a third of the conflict-crippled country.

But the question of whether the goal of self-sufficiency has been achieved is seemingly subjective.

"On paper, Iraq should have a small fleet of premium multirole aircraft for its national security needs," said Miguel Miranda, an expert analyst in global military technology. "But whether or not Iraqi airpower grows in the 2020s is wholly dependent on the state budget, which is itself determined by the price of oil. If the Iraqi government can't sustain spending on its air force to keep what it already has in flyable condition, there are many examples of countries whose air power withered to nothing."

Iraqi leaders descended on Washington last week for critical talks regarding the future of U.S. military aid in the volatile region, which was strained after the Solemani killing and threats from some top Baghdad officials to kick out American troops.

President Donald J. Trump, joined by Vice President Mike Pence, meets with senior White House advisors Tuesday evening, Jan. 7, 2020, in the Situation Room of the White House, on a further meeting about the Islamic Republic of Iran missile attacks on U.S. military facilities in Iraq.

President Donald J. Trump, joined by Vice President Mike Pence, meets with senior White House advisors Tuesday evening, Jan. 7, 2020, in the Situation Room of the White House, on a further meeting about the Islamic Republic of Iran missile attacks on U.S. military facilities in Iraq. (Official White House Photo by Shealah Craighead)

However, U.S. Central Commander Gen. Frank McKenzie has called the latest dialogue "healthy."

"We don't want to maintain a huge number of soldiers forever in Iraq. We want to get smaller," he said in a U.S. Institute of Peace online event this month, but he said the Iraqi forces are ready to take on the fight by themselves.

President Trump has also remained committed to his long-running pledge to bring the troops home from Iraq and put a stop to "endless wars," and over the weekend, the U.S. formally pulled out of the Taji military base near Baghdad, signing it back over to the Iraqi security forces. Yet Iraq's new prime minister, Mustafa Al-Kadhimi, has maintained that the country still needs "cooperation and assistance" on the ground, in keeping with the "changing nature of terrorism's threat."

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According to some U.S. defense experts, the onus is on Baghdad to foster a secure environment.

"Maintenance has long been an Achilles heel for the Iraqi security services, and they have been almost entirely dependent on the United States to keep their planes flying," John Hannah, a national security adviser for former Vice President Dick Cheney and a senior counselor at the Foundation for Defense of Democracies (FDD), told Fox News.

"The F-16s have been based at the Balad airfield, which has been regularly targeted with rockets and mortars by pro-Iranian militias. My view is that the F-16 program could be in serious trouble if the Iraqi government is unable or unwilling to fulfill its most basic international obligation to protect U.S. diplomats, troops, and contractors that they've invited into their country."