The U.S. Air Force has certified Space Exploration Technologies Corp. to launch military satellites, ending a Lockheed Martin Corp.-Boeing Co. joint venture’s decade-long monopoly on the business.

The decision, announced late Tuesday, is a significant win for the start-up rocket-maker, known as SpaceX and headed by billionaire Elon Musk, and a loss for the joint venture, called United Launch Alliance LLC.

“This is an important step toward bringing competition to National Security Space launch,” Musk said in a release. “We thank the Air Force for its confidence in us and look forward to serving it well.”

Air Force Secretary Deborah Lee James hailed the approval as an “important milestone” for both the service and Defense Department, which blessed the 2006 creation of a sole supplier for its launch needs.

“SpaceX’s emergence as a viable commercial launch provider provides the opportunity to compete launch services for the first time in almost a decade,” she said in the release. “Ultimately, leveraging of the commercial space market drives down cost to the American taxpayer and improves our military’s resiliency.”

The certification process was overseen by Lt. Gen. Samuel Greaves, commander of the Air Force Space and Missile Systems Center and the service’s executive officer for space. The effort took two years, cost more than $60 million and involved 150 people and several hundred audits.

As a result, SpaceX’s Falcon 9 rocket is now certified to launch national-security satellites under the Evolved Expendable Launch Vehicle, or EELV, program. The firm will be eligible to compete for missions as early as June, when the Air Force is expected to release a request for proposals to launch its GPS III satellite. It sells for about $60 million per launch, though the price would be higher for military missions because of the additional requirements.

“The SpaceX and SMC teams have worked hard to achieve certification,” Greaves said in the release. “Our intent is to promote the viability of multiple EELV-class launch providers as soon as feasible.”

Musk and his company led a bruising campaign against ULA for its high cost of launch and use of Russian technology. The latter criticism found an increasingly receptive audience in the Pentagon and on Capitol Hill last year after pro-Russian forces invaded and took over Crimea in Ukraine.

ULA hit back, charging SpaceX with instigating an imbroglio between the U.S. and Russia over the sale of RD-180 rocket engines, GPS satellites and even missions to the International Space Station. It also changed leadership at the top, with Tory Bruno replacing Michael Gass as chief executive officer.

SpaceX, meanwhile, also challenged the Air Force for its unique relationship with ULA. The company sued the service over a contract it awarded to the joint venture for a so-called “bulk-buy” of 36 cores — the main part of a rocket including the engine – through 2017. SpaceX later dropped its complaint after the Air Force pledged to open more launches to competition.

While ULA’s Bruno has said he welcomes the arrival of a competitor in the military market, he has warned of a coming slump in defense launches. He has also said to remain viable ULA will need more commercial and civilian deals, as well as approval from Congress to buy more Russian-made RD-180 engines until a domestic alternative is ready.

ULA’s planned Vulcan rocket would use a reusable engine called the BE-4, developed by Blue Origin LLC, owned by Amazon.com-founder Jeff Bezos. It could also use the AR-1, a liquid oxygen and kerosene-fueled propulsion system being developed by Aerojet Rocketdyne. It would sell for less than $100 million be ready for missions in 2019.