The Boeing KC-46 is a military aerial refueling and strategic transport aircraft developed by Boeing from its767 jet airliner. In February 2011, the tanker was selected by the United States Air Force (USAF) as the winner in the KC-X tanker competition to replace older KC-135 Stratotankers.

Development
Background
The U.S. Air Force ran a procurement program to replace around 100 of its oldest KC-135E Stratotankers, and selected Boeing's KC-767. The Boeing tanker received the KC-767A designation from the United States Department of Defense in 2002 and appearing in the 2004 edition of DoD model designation report. The Air Force decided to lease 100 KC-767 tankers from Boeing.

Despite several nations leasing military aircraft, there was criticism. U.S. Senator John McCain and others criticized the draft leasing agreement as being wasteful and problematic. In response to the protests, the Air Force struck a compromise in November 2003, whereby it would purchase 80 KC-767 aircraft and lease 20 more.

Then in December 2003, the Pentagon announced the project was to be frozen when an investigation of allegations of corruption led to the jailing of one of its former procurement executives who applied to work for Boeing.

USAF KC-X Program
In 2006 the USAF released a request for proposal (RFP) for a new tanker program, KC-X, to be selected by 2007. Boeing had also announced it may enter an even higher capability tanker based on the Boeing 777, named the KC-777 Strategic Tanker.Airbus partnered with Northrop Grumman to offer the Airbus A330 MRTT, the tanker version of the A330, which was being marketed to the USAF under the company name, KC-30.

In late January 2007 the USAF issued the KC-X Aerial Refueling Aircraft Request for Proposal. The RFP called for 179 (4 system development and demonstration and 175 production) tankers, in a contract worth an estimated US$40 billion. However, Northrop and EADS expressed their displeasure at how the RFP was structured and threatened to withdraw, leaving only Boeing to offer an aircraft.

On 12 February 2007, Boeing announced it was offering the KC-767 Advanced Tanker for the KC-X Tanker competition. Boeing stated that for KC-X's requirements, the KC-767 was a better fit than the KC-777. On 11 April 2007, Boeing submitted its KC-767 tanker proposal to U.S. Air Force. The KC-767 Advanced Tanker offered for this KC-X round was based on the in-development 767-200LRF (Long Range Freighter), rather than the -200ER on which Italian and Japanese KC-767 aircraft are based differing by combining the -200ER fuselage, -300F wing, gear, cargo door and floor, -400ER digital flightdeck and flaps, uprated engines, and "sixth-generation" fly-by-wire fuel delivery boom. The KC-767 uses manual flight control, allowing unrestricted maneuverability to avoid threats anywhere in the flight envelope.

Boeing submitted the final version of its proposal on 3 January 2008. On 29 February 2008, the DoD chose the Northrop Grumman/EADS KC-30, over the KC-767. The KC-30 was subsequently designated KC-45A by the Air Force. Boeing submitted a protest to the United States Government Accountability Office on 11 March 2008 and began waging a public relations campaign in support of their protest. On 18 June, following a series of admissions by the Air Force on the flaws in the bidding process, the GAO upheld Boeing's protest and recommended the contract be rebid. On 9 July 2008, Defense Secretary Robert Gates announced that the Air Force would reopen bidding on the tanker contract. Secretary Gates put the contract for the KC-45 into an "expedited recompetition" with Defense Undersecretary John Young in charge of the selection process instead of the Air Force. A draft of the revised RFP was provided to the contractors on 6 August 2008 for comments. By mid-August the revised RFP was to be finalized. However, on 10 September 2008, the U.S. Defense Department canceled the KC-X solicitation.

On 24 September 2009, the USAF began the first steps in the new round of bids, with a clearer set of criteria, including reducing the number of requirements from 800 to 373 in an attempt to simplify the process and allow a more objective decision to be made. On 4 March 2010, Boeing announced it would bid the KC-767 tanker for the new KC-X round. EADS announced in April 2010 it would submit a tanker bid without Northrop Grumman as a U.S. partner. Boeing submitted its KC-767 "NewGen Tanker" bid on 9 July 2010. The company submitted a revised bid on 10 February 2011.

On 24 February 2011, the Air Force announced the selection of Boeing's KC-767. The aircraft will receive the designation KC-46A. Boeing was also awarded a development contract for the tanker. The contract calls for Boeing to complete and deliver 18 initial operational KC-46 tankers by 2017. The Air Force is seeking to receive a total of 179 new tankers. Boeing's "NewGen Tanker" is based on the 767-200 with an improved version of the KC-10 refueling boom, and cockpit displays from the 787.

In late June 2011, it was reported that development costs were projected to overrun by about $300 million. Boeing would be responsible for this amount, which exceeds the contract cost cap of $4.9 billion. In July 2011, revised cost projections indicated a reduced cost overrun. In March 2013, the program cost for development and procurement of 179 tankers was projected to total US$44.78 billion.

In 2013 in response to a review that showed that current plans did not take full advantage of the KC-46's cargo and aeromedical evacuation advantages over the KC-135, the USAF added additional crews and flight hours for the aircraft to their future plans.

On 21 August 2013, Boeing and the Air Force completed a critical design review (CDR) for the KC-46. The CDR was held from July 8-10, and was completed one month ahead of the original schedule, which planned on the review to be finished on 24 September. With the CDR complete, the KC-46 design is now set and production and testing can proceed. Assembling of the wing for the first aircraft began on 26 June 2013. Flight testing of the Boeing 767-2C airframe, which will be reconfigured into the KC-46, is scheduled to begin in mid-2014. The first fully-equipped KC-46 tanker is projected to fly in early 2015. Boeing is contracted to build four test aircraft and deliver 18 combat-ready tankers by August 2017. The Air Force is to buy 179 KC-46s, with all delivered by 2028.